Load packages

library(rio) # r package to import or export dataset
library(tidyverse) # r package to wrangle dataset
## ── Attaching core tidyverse packages ──────────────────────── tidyverse 2.0.0 ──
## ✔ dplyr     1.1.4     ✔ readr     2.1.6
## ✔ forcats   1.0.1     ✔ stringr   1.6.0
## ✔ ggplot2   4.0.1     ✔ tibble    3.3.1
## ✔ lubridate 1.9.4     ✔ tidyr     1.3.2
## ✔ purrr     1.2.1     
## ── Conflicts ────────────────────────────────────────── tidyverse_conflicts() ──
## ✖ dplyr::filter() masks stats::filter()
## ✖ dplyr::lag()    masks stats::lag()
## ℹ Use the conflicted package (<http://conflicted.r-lib.org/>) to force all conflicts to become errors
library(psych) # r package  to calculate internal consistency
## 
## Attaching package: 'psych'
## 
## The following objects are masked from 'package:ggplot2':
## 
##     %+%, alpha
library(irr) # r package to calculate inter-rater reliability
## Loading required package: lpSolve

Task 1-1. Calculate Cronbach’s alpha (Q1 - Q16)

We will use the same dataset (Nerdy scale) used in class, “ITLS_4160_internal_consistency.xlsx.”

Calculate Cronbach’s alpha for 16 items (Q1–Q16).

Load dataset

nerdy_data <- import("ITLS_4160_internal_consistency.xlsx")
head(nerdy_data)
##   Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 Q19 Q20 Q21
## 1  3  5  3  3  5  5  5  3  5   5   4   5   5   5   3   5   4   5   5   5   5
## 2  4  4  4  3  5  2  5  1  4   4   1   5   4   4   1   3   3   3   1   3   3
## 3  5  5  5  5  5  5  5  5  5   5   5   4   5   5   4   5   5   4   5   5   5
## 4  5  5  5  5  5  5  5  3  5   5   5   5   4   4   4   2   5   5   5   5   4
## 5  4  4  4  4  4  4  4  4  4   5   4   4   5   5   1   1   5   5   3   5   5
## 6  4  4  4  4  4  4  5  3  3   4   4   4   3   5   3   4   3   4   5   4   4
##   Q22 Q23 Q24 Q25 Q26 country introelapse testelapse surveyelapse race_arab
## 1   5   5   5   5   5      US          41         93          125         0
## 2   3   4   4   4   5      GB          13        131          161         0
## 3   5   5   5   3   5      PL           2         49           87         0
## 4   1   5   5   5   5      US          26        710          228         0
## 5   4   4   5   4   0      US           6        195          424         0
## 6   2   5   5   3   4      US         410        117          113         0
##   race_asian race_black race_white race_hispanic race_nativeam race_nativeau
## 1          0          0          1             0             0             0
## 2          0          0          1             0             0             0
## 3          0          0          1             0             0             0
## 4          0          0          1             0             0             0
## 5          0          0          1             0             0             0
## 6          0          0          1             0             0             0
##   race_other nerdy ASD
## 1          0     7   2
## 2          0     6   2
## 3          0     7   2
## 4          0     7   2
## 5          0     6   2
## 6          0     5   2

Step 1: Explore data (Q1 - Q16)

nerdy_data %>%
  select(Q1:Q16) %>%
  describe ()
##     vars    n mean   sd median trimmed  mad min max range  skew kurtosis   se
## Q1     1 1000 3.93 1.11      4    4.10 1.48   0   5     5 -1.05     0.58 0.04
## Q2     2 1000 4.00 1.25      4    4.21 1.48   0   5     5 -1.18     0.40 0.04
## Q3     3 1000 4.17 1.06      4    4.38 1.48   0   5     5 -1.49     1.94 0.03
## Q4     4 1000 3.73 1.26      4    3.88 1.48   0   5     5 -0.73    -0.50 0.04
## Q5     5 1000 3.81 1.22      4    3.97 1.48   0   5     5 -0.91    -0.04 0.04
## Q6     6 1000 3.66 1.20      4    3.79 1.48   0   5     5 -0.68    -0.31 0.04
## Q7     7 1000 4.13 1.14      4    4.35 1.48   0   5     5 -1.40     1.35 0.04
## Q8     8 1000 3.80 1.36      4    4.00 1.48   0   5     5 -0.93    -0.35 0.04
## Q9     9 1000 3.93 1.11      4    4.09 1.48   0   5     5 -0.95     0.28 0.04
## Q10   10 1000 4.08 1.05      4    4.24 1.48   0   5     5 -1.17     1.11 0.03
## Q11   11 1000 3.14 1.57      3    3.18 2.97   0   5     5 -0.21    -1.47 0.05
## Q12   12 1000 3.80 1.25      4    3.97 1.48   0   5     5 -0.89    -0.16 0.04
## Q13   13 1000 3.65 1.32      4    3.80 1.48   0   5     5 -0.60    -0.77 0.04
## Q14   14 1000 3.63 1.20      4    3.74 1.48   0   5     5 -0.58    -0.49 0.04
## Q15   15 1000 2.94 1.51      3    2.93 1.48   0   5     5 -0.01    -1.41 0.05
## Q16   16 1000 3.48 1.42      4    3.60 1.48   0   5     5 -0.47    -1.11 0.04

Step 2: Calculate Cronbach’s alpha (Q1 - Q16)

nerdy_data %>%
  select(Q1:Q16) %>%
  alpha()
## 
## Reliability analysis   
## Call: alpha(x = .)
## 
##   raw_alpha std.alpha G6(smc) average_r S/N    ase mean   sd median_r
##        0.8       0.8    0.82       0.2   4 0.0094  3.7 0.63     0.19
## 
##     95% confidence boundaries 
##          lower alpha upper
## Feldt     0.78   0.8  0.82
## Duhachek  0.78   0.8  0.82
## 
##  Reliability if an item is dropped:
##     raw_alpha std.alpha G6(smc) average_r S/N alpha se var.r med.r
## Q1       0.78      0.79    0.81      0.20 3.7   0.0101 0.011  0.18
## Q2       0.79      0.79    0.81      0.20 3.8   0.0099 0.012  0.20
## Q3       0.79      0.79    0.82      0.20 3.8   0.0098 0.011  0.19
## Q4       0.78      0.79    0.81      0.20 3.7   0.0102 0.011  0.18
## Q5       0.79      0.79    0.81      0.20 3.8   0.0098 0.011  0.18
## Q6       0.79      0.79    0.81      0.20 3.8   0.0099 0.012  0.19
## Q7       0.79      0.79    0.81      0.20 3.9   0.0097 0.010  0.19
## Q8       0.78      0.79    0.81      0.20 3.7   0.0101 0.011  0.18
## Q9       0.79      0.79    0.81      0.20 3.8   0.0098 0.011  0.18
## Q10      0.79      0.79    0.82      0.20 3.9   0.0097 0.012  0.18
## Q11      0.79      0.80    0.82      0.21 3.9   0.0096 0.012  0.19
## Q12      0.79      0.79    0.81      0.20 3.7   0.0099 0.011  0.19
## Q13      0.78      0.79    0.81      0.20 3.7   0.0102 0.012  0.18
## Q14      0.79      0.79    0.82      0.20 3.8   0.0098 0.012  0.19
## Q15      0.79      0.80    0.82      0.21 3.9   0.0096 0.011  0.19
## Q16      0.79      0.79    0.82      0.20 3.8   0.0098 0.011  0.19
## 
##  Item statistics 
##        n raw.r std.r r.cor r.drop mean  sd
## Q1  1000  0.57  0.57  0.55   0.49  3.9 1.1
## Q2  1000  0.50  0.49  0.44   0.40  4.0 1.2
## Q3  1000  0.47  0.48  0.42   0.38  4.2 1.1
## Q4  1000  0.57  0.58  0.55   0.48  3.7 1.3
## Q5  1000  0.49  0.51  0.46   0.39  3.8 1.2
## Q6  1000  0.49  0.51  0.46   0.39  3.7 1.2
## Q7  1000  0.44  0.46  0.42   0.35  4.1 1.1
## Q8  1000  0.56  0.54  0.50   0.45  3.8 1.4
## Q9  1000  0.48  0.51  0.47   0.39  3.9 1.1
## Q10 1000  0.43  0.46  0.39   0.34  4.1 1.0
## Q11 1000  0.47  0.44  0.37   0.34  3.1 1.6
## Q12 1000  0.52  0.53  0.49   0.42  3.8 1.2
## Q13 1000  0.57  0.57  0.54   0.47  3.6 1.3
## Q14 1000  0.48  0.49  0.43   0.38  3.6 1.2
## Q15 1000  0.46  0.43  0.37   0.33  2.9 1.5
## Q16 1000  0.49  0.48  0.42   0.38  3.5 1.4
## 
## Non missing response frequency for each item
##        0    1    2    3    4    5 miss
## Q1  0.00 0.05 0.06 0.17 0.36 0.37    0
## Q2  0.00 0.06 0.08 0.11 0.26 0.48    0
## Q3  0.00 0.04 0.05 0.10 0.33 0.48    0
## Q4  0.00 0.07 0.12 0.17 0.28 0.36    0
## Q5  0.00 0.06 0.10 0.15 0.33 0.35    0
## Q6  0.00 0.06 0.11 0.22 0.31 0.30    0
## Q7  0.01 0.04 0.06 0.10 0.29 0.50    0
## Q8  0.00 0.10 0.10 0.11 0.28 0.42    0
## Q9  0.00 0.03 0.08 0.17 0.33 0.38    0
## Q10 0.00 0.03 0.04 0.18 0.30 0.44    0
## Q11 0.00 0.26 0.10 0.15 0.21 0.28    0
## Q12 0.00 0.06 0.11 0.14 0.31 0.37    0
## Q13 0.00 0.09 0.12 0.22 0.21 0.37    0
## Q14 0.00 0.06 0.12 0.23 0.29 0.29    0
## Q15 0.00 0.26 0.16 0.17 0.20 0.21    0
## Q16 0.00 0.14 0.14 0.17 0.22 0.33    0

Step 3: Interpretation of Cronbach’s alpha

Let’s interpret Cronbach’s α, based on Nunally (1978)’s interpretation guideline.

  • ≥ .90: Excellent (but may indicate item redundancy)

  • .80 – .89: Good

  • .70 – .79: Acceptable

  • .60 – .69: Questionable

  • .50 – .59: Poor

  • < .50: Unacceptable

Interpretation: Sixteen items (Q1 - Q16) of the Nerdy Personality Attributes Scale yielded [put your interpretation!]

The alpha score averages .8 for 16 items of data. This falls under the Good score. This means that the internal consistency is working together. This shows that the majority of the items correlate with each other.
# Task 1-2. Calculate Cronbach’s alpha (Q1 - Q26)

We will use the same dataset (Nerdy scale) used in class, “ITLS_4160_internal_consistency.xlsx.”, but please calculate Cronbach’s alpha for all 26 items (Q1–Q26).

Step 1: Explore data (Q1 - Q26)

nerdy_data %>%
  select(Q1:Q26) %>%
  describe()
##     vars    n mean   sd median trimmed  mad min max range  skew kurtosis   se
## Q1     1 1000 3.93 1.11      4    4.10 1.48   0   5     5 -1.05     0.58 0.04
## Q2     2 1000 4.00 1.25      4    4.21 1.48   0   5     5 -1.18     0.40 0.04
## Q3     3 1000 4.17 1.06      4    4.38 1.48   0   5     5 -1.49     1.94 0.03
## Q4     4 1000 3.73 1.26      4    3.88 1.48   0   5     5 -0.73    -0.50 0.04
## Q5     5 1000 3.81 1.22      4    3.97 1.48   0   5     5 -0.91    -0.04 0.04
## Q6     6 1000 3.66 1.20      4    3.79 1.48   0   5     5 -0.68    -0.31 0.04
## Q7     7 1000 4.13 1.14      4    4.35 1.48   0   5     5 -1.40     1.35 0.04
## Q8     8 1000 3.80 1.36      4    4.00 1.48   0   5     5 -0.93    -0.35 0.04
## Q9     9 1000 3.93 1.11      4    4.09 1.48   0   5     5 -0.95     0.28 0.04
## Q10   10 1000 4.08 1.05      4    4.24 1.48   0   5     5 -1.17     1.11 0.03
## Q11   11 1000 3.14 1.57      3    3.18 2.97   0   5     5 -0.21    -1.47 0.05
## Q12   12 1000 3.80 1.25      4    3.97 1.48   0   5     5 -0.89    -0.16 0.04
## Q13   13 1000 3.65 1.32      4    3.80 1.48   0   5     5 -0.60    -0.77 0.04
## Q14   14 1000 3.63 1.20      4    3.74 1.48   0   5     5 -0.58    -0.49 0.04
## Q15   15 1000 2.94 1.51      3    2.93 1.48   0   5     5 -0.01    -1.41 0.05
## Q16   16 1000 3.48 1.42      4    3.60 1.48   0   5     5 -0.47    -1.11 0.04
## Q17   17 1000 3.86 1.17      4    4.02 1.48   0   5     5 -0.90     0.05 0.04
## Q18   18 1000 3.89 1.35      4    4.12 1.48   0   5     5 -1.06    -0.12 0.04
## Q19   19 1000 3.42 1.56      4    3.52 1.48   0   5     5 -0.43    -1.35 0.05
## Q20   20 1000 3.62 1.18      4    3.72 1.48   0   5     5 -0.48    -0.60 0.04
## Q21   21 1000 2.97 1.63      3    2.96 2.97   0   5     5 -0.02    -1.61 0.05
## Q22   22 1000 2.42 1.38      2    2.28 1.48   0   5     5  0.57    -0.94 0.04
## Q23   23 1000 3.85 1.38      4    4.07 1.48   0   5     5 -0.95    -0.39 0.04
## Q24   24 1000 4.24 0.99      5    4.42 0.00   0   5     5 -1.57     2.63 0.03
## Q25   25 1000 3.10 1.41      3    3.13 1.48   0   5     5 -0.17    -1.26 0.04
## Q26   26 1000 4.07 1.11      4    4.26 1.48   0   5     5 -1.16     0.64 0.04

Step 2: Calculate Cronbach’s alpha (Q1 - Q26)

nerdy_data %>%
  select(Q1:Q26) %>%
  alpha()
## 
## Reliability analysis   
## Call: alpha(x = .)
## 
##   raw_alpha std.alpha G6(smc) average_r S/N    ase mean   sd median_r
##       0.85      0.86    0.88      0.19   6 0.0069  3.7 0.59     0.18
## 
##     95% confidence boundaries 
##          lower alpha upper
## Feldt     0.84  0.85  0.86
## Duhachek  0.84  0.85  0.86
## 
##  Reliability if an item is dropped:
##     raw_alpha std.alpha G6(smc) average_r S/N alpha se var.r med.r
## Q1       0.84      0.85    0.88      0.18 5.6   0.0072 0.013  0.17
## Q2       0.84      0.85    0.88      0.19 5.7   0.0071 0.013  0.18
## Q3       0.85      0.85    0.88      0.19 5.8   0.0071 0.013  0.18
## Q4       0.84      0.85    0.88      0.18 5.6   0.0072 0.013  0.17
## Q5       0.84      0.85    0.88      0.18 5.6   0.0072 0.013  0.17
## Q6       0.84      0.85    0.88      0.18 5.6   0.0072 0.013  0.17
## Q7       0.85      0.85    0.88      0.19 5.7   0.0071 0.013  0.18
## Q8       0.84      0.85    0.88      0.19 5.7   0.0072 0.013  0.17
## Q9       0.84      0.85    0.88      0.18 5.6   0.0072 0.012  0.17
## Q10      0.85      0.85    0.88      0.19 5.8   0.0071 0.014  0.17
## Q11      0.85      0.85    0.88      0.19 5.8   0.0071 0.013  0.18
## Q12      0.84      0.85    0.88      0.18 5.6   0.0072 0.013  0.17
## Q13      0.84      0.85    0.87      0.18 5.6   0.0073 0.013  0.17
## Q14      0.84      0.85    0.88      0.18 5.7   0.0072 0.013  0.17
## Q15      0.85      0.85    0.88      0.19 5.9   0.0070 0.013  0.18
## Q16      0.84      0.85    0.88      0.19 5.8   0.0071 0.013  0.18
## Q17      0.84      0.85    0.88      0.18 5.7   0.0072 0.013  0.18
## Q18      0.85      0.86    0.88      0.19 6.0   0.0069 0.013  0.18
## Q19      0.85      0.86    0.88      0.19 5.9   0.0069 0.012  0.18
## Q20      0.84      0.85    0.88      0.19 5.7   0.0072 0.013  0.17
## Q21      0.85      0.85    0.88      0.19 5.9   0.0070 0.013  0.18
## Q22      0.84      0.85    0.88      0.19 5.7   0.0071 0.013  0.18
## Q23      0.84      0.85    0.88      0.19 5.7   0.0072 0.013  0.17
## Q24      0.84      0.85    0.88      0.18 5.7   0.0072 0.013  0.17
## Q25      0.85      0.85    0.88      0.19 5.8   0.0070 0.013  0.18
## Q26      0.84      0.85    0.88      0.18 5.6   0.0072 0.013  0.17
## 
##  Item statistics 
##        n raw.r std.r r.cor r.drop mean   sd
## Q1  1000  0.52  0.52  0.50   0.46  3.9 1.11
## Q2  1000  0.46  0.45  0.42   0.39  4.0 1.25
## Q3  1000  0.40  0.41  0.38   0.34  4.2 1.06
## Q4  1000  0.53  0.53  0.51   0.46  3.7 1.26
## Q5  1000  0.52  0.53  0.51   0.45  3.8 1.22
## Q6  1000  0.52  0.54  0.51   0.46  3.7 1.20
## Q7  1000  0.43  0.45  0.43   0.37  4.1 1.14
## Q8  1000  0.51  0.49  0.47   0.44  3.8 1.36
## Q9  1000  0.52  0.54  0.53   0.47  3.9 1.11
## Q10 1000  0.42  0.45  0.41   0.37  4.1 1.05
## Q11 1000  0.45  0.41  0.39   0.36  3.1 1.57
## Q12 1000  0.51  0.52  0.50   0.44  3.8 1.25
## Q13 1000  0.57  0.58  0.56   0.51  3.6 1.32
## Q14 1000  0.49  0.50  0.47   0.42  3.6 1.20
## Q15 1000  0.40  0.37  0.33   0.32  2.9 1.51
## Q16 1000  0.46  0.44  0.41   0.38  3.5 1.42
## Q17 1000  0.50  0.50  0.48   0.44  3.9 1.17
## Q18 1000  0.31  0.32  0.26   0.23  3.9 1.35
## Q19 1000  0.36  0.33  0.30   0.27  3.4 1.56
## Q20 1000  0.48  0.49  0.46   0.41  3.6 1.18
## Q21 1000  0.40  0.37  0.33   0.31  3.0 1.63
## Q22 1000  0.45  0.45  0.42   0.38  2.4 1.38
## Q23 1000  0.50  0.50  0.47   0.43  3.9 1.38
## Q24 1000  0.48  0.51  0.48   0.43  4.2 0.99
## Q25 1000  0.39  0.39  0.35   0.31  3.1 1.41
## Q26 1000  0.51  0.53  0.51   0.45  4.1 1.11
## 
## Non missing response frequency for each item
##        0    1    2    3    4    5 miss
## Q1  0.00 0.05 0.06 0.17 0.36 0.37    0
## Q2  0.00 0.06 0.08 0.11 0.26 0.48    0
## Q3  0.00 0.04 0.05 0.10 0.33 0.48    0
## Q4  0.00 0.07 0.12 0.17 0.28 0.36    0
## Q5  0.00 0.06 0.10 0.15 0.33 0.35    0
## Q6  0.00 0.06 0.11 0.22 0.31 0.30    0
## Q7  0.01 0.04 0.06 0.10 0.29 0.50    0
## Q8  0.00 0.10 0.10 0.11 0.28 0.42    0
## Q9  0.00 0.03 0.08 0.17 0.33 0.38    0
## Q10 0.00 0.03 0.04 0.18 0.30 0.44    0
## Q11 0.00 0.26 0.10 0.15 0.21 0.28    0
## Q12 0.00 0.06 0.11 0.14 0.31 0.37    0
## Q13 0.00 0.09 0.12 0.22 0.21 0.37    0
## Q14 0.00 0.06 0.12 0.23 0.29 0.29    0
## Q15 0.00 0.26 0.16 0.17 0.20 0.21    0
## Q16 0.00 0.14 0.14 0.17 0.22 0.33    0
## Q17 0.00 0.04 0.10 0.17 0.31 0.37    0
## Q18 0.00 0.10 0.07 0.10 0.26 0.46    0
## Q19 0.00 0.19 0.12 0.13 0.17 0.38    0
## Q20 0.00 0.05 0.12 0.27 0.26 0.29    0
## Q21 0.00 0.30 0.14 0.09 0.20 0.27    0
## Q22 0.00 0.34 0.24 0.17 0.13 0.12    0
## Q23 0.01 0.09 0.11 0.11 0.22 0.47    0
## Q24 0.00 0.02 0.03 0.12 0.32 0.51    0
## Q25 0.00 0.19 0.17 0.19 0.25 0.20    0
## Q26 0.00 0.03 0.08 0.13 0.29 0.47    0

Step 3: Interpretation of Cronbach’s alpha

Let’s interpret Cronbach’s α, based on Nunally (1978)’s interpretation guideline.

  • ≥ .90: Excellent (but may indicate item redundancy)

  • .80 – .89: Good

  • .70 – .79: Acceptable

  • .60 – .69: Questionable

  • .50 – .59: Poor

  • < .50: Unacceptable

Interpretation: Twenty-six items (Q1 - Q26) of the Nerdy Personality Attributes Scale yielded [put your interpretation!]. The alpha for all 26 items is between .86-ish. This means that the greater the points of data in a test, the higher the accuracy that the items have good internal consistency.

Task 1-3. Let’s synthesize what you learned.

How did internal consistency vary with the increase in the number of items?

  • Q1 - Q6 (6 items): Cronbach’s alpha = .7

  • Q1 - Q16 (16 items): Cronbach’s alpha = .8

  • Q1 - Q26 (26 items): Cronbach’s alpha =.86

Please check T/F based on the description:

  • Q1: The more items a scale has, the higher Cronbach’s alpha value is: T or F?

True. This is mostly true as long as the items are somewhat related. Cronbach’s alpha is influenced by 2 things: avergae correlation between items, and number of items on the scale. However, if nbew items are added that are poorly related, then the alpha won’t necessarily go up.

  • Q2: The reliability of a test is independent of the sample and test features: T or F?

False. Reliability is not independent of the sample or test features. Reliability can change depending on who takes the test, and the variability of the test scores. The more variability–> often higher reliability.Less variability often means lower reliability. Change the test, change the reliability.

Task 2-1. Calculate Cohen’s Kappa between Rater 1 and Rater 3

We will use the same dataset (Nerdy scale) used in class, “ITLS_4160_Inter_rater_reliability.xlsx.”

Let’s calculate the inter-rater reliability between Rater 1 and Rater 3.

Load data

writing_scores <- import("ITLS_4160_Inter_rater_reliability.xlsx")
head(writing_scores)
##   Person Rater1 Rater2 Rater3
## 1      1      1      1      1
## 2      2      2      1      3
## 3      3      2      2      3
## 4      4      3      3      4
## 5      5      3      2      4
## 6      6      3      3      4

Step 1: Explore data (Rater1 and Rater3)

writing_scores %>%
  select(Rater1, Rater3) %>%
  describe()
##        vars  n mean   sd median trimmed  mad min max range  skew kurtosis   se
## Rater1    1 10  3.2 1.32      3    3.25 1.48   1   5     4 -0.06    -1.36 0.42
## Rater3    2 10  3.8 1.23      4    4.00 1.48   1   5     4 -0.96     0.00 0.39

Step 2: Calculate inter-rater reliability (Rater1 and Rater3)

writing_scores %>%
select(Rater1, Rater3) %>%
  kappa2()
##  Cohen's Kappa for 2 Raters (Weights: unweighted)
## 
##  Subjects = 10 
##    Raters = 2 
##     Kappa = 0.241 
## 
##         z = 1.58 
##   p-value = 0.113

Step 3: Interpretation of Cohen’s kappa

Please interpret inter-rater reliability between Rater 1 and Rater 3 based on Landis & Koch (1977)’s interpretation guideline.

  • < 0.00 Poor agreement

  • 0.00 – 0.20 Slight agreement

  • 0.21 – 0.40 Fair agreement

  • 0.41 – 0.60 Moderate agreement

  • 0.61 – 0.80 Substantial agreement

  • 0.81 – 1.00 Almost perfect agreement

Interpretation: Cohen’s kappa indicated [put your interpretation] , according to Landis and Koch’s (1977) guideline.

The kappa score between rater1 and rater3 was .24. This indicates a fair agreement. If you have several questions that are supposed to measure one construct, Cronbach’s alpha tells you whether those questions are working together. A score like this is fair, but not substantial or almost perfect. Alpha can be inflated by too many items, very similar, or almost duplicate questions. It is also used well for data that is continuous or a likert-type scale.

Task 2-2. Calculate Cohen’s Kappa between Rater 2 and Rater 3

We will use the same dataset (Nerdy scale) used in class, “ITLS_4160_Inter_rater_reliability.xlsx.”

Let’s calculate the inter-rater reliability between Rater 2 and Rater 3.

Step 1: Explore data (Rater2 and Rater3)

Step 2: Calculate inter-rater reliability (Rater2 and Rater3)

writing_scores %>%
  select(Rater2, Rater3) %>%
  kappa2()
##  Cohen's Kappa for 2 Raters (Weights: unweighted)
## 
##  Subjects = 10 
##    Raters = 2 
##     Kappa = 0.268 
## 
##         z = 1.96 
##   p-value = 0.0504

Step 3: Interpretation of Cohen’s kappa

Please interpret inter-rater reliability between Rater 2 and Rater 3 based on Landis & Koch (1977)’s interpretation guideline.

  • < 0.00 Poor agreement

  • 0.00 – 0.20 Slight agreement

  • 0.21 – 0.40 Fair agreement

  • 0.41 – 0.60 Moderate agreement

  • 0.61 – 0.80 Substantial agreement

  • 0.81 – 1.00 Almost perfect agreement

Interpretation: Cohen’s kappa indicated [put your interpretation] , according to Landis and Koch’s (1977) guideline.

Once again the inter-relatability is only .27, or fair agreement. This means that the relatedness of the rater scores are fair in agreement, beyond chance.