W6 Test 3 Denpen T-Test

ASSIGNMENT 6 RESEARCH SCENARIO 3

Assess the difference in employees communication skills before and after attend the professional conmmunication training

HYPOTHESES:

H0: There is no difference in employees communication skills before and after attend the professional conmmunication training

H1: Employees communication skill is improved after attend the communication training

R PROCESS

IMPORT EXCEL FILE CODE

library(readxl)

A6R3 <- read_excel("D:/000 20251021 AA 5221 Applied Analytics & Methods 1/Week 6/A6R3.xlsx")

# CALCULATE THE DIFFERENCE SCORES

Before <- A6R3$PreTraining
After <- A6R3$PostTraining

Differences <- After - Before

CHECK THE NORMALITY OF THE DIFFERENCE

CREATE A HISTOGRAM FOR THE DIFFERENCE

hist(Differences,
     main = "Histogram of Difference Before and After training",
     xlab = "Value",
     ylab = "Frequency",
     col = "blue",
     border = "black",
     breaks = 20)

Histogram of data of difference between before and after training is normally distributed

SHAPIRO-WILK TEST

shapiro.test(Differences)

## 
##  Shapiro-Wilk normality test
## 
## data:  Differences
## W = 0.98773, p-value = 0.21

The data is normally distributed, p > .05

CREATE BOX PLOTS

boxplot(Differences,
        main = "Distribution of Score Differences (After - Before)",
        ylab = "Difference in Scores",
        col = "blue",
        border = "darkblue")

There is not dot outside of the whiskers

DESCRIPTIVE STATISTIC

mean(Before, na.rm = TRUE)

## [1] 59.73333

median(Before, na.rm = TRUE)

## [1] 60

sd(Before, na.rm = TRUE)

## [1] 7.966091

length(Before)

## [1] 150

mean(After, na.rm = TRUE)

## [1] 69.24

median(After, na.rm = TRUE)

## [1] 69.5

sd(After, na.rm = TRUE)

## [1] 9.481653

length(After)

## [1] 150

DEPENDENT T-TEST

t.test(Before, After, paired = TRUE)

## 
##  Paired t-test
## 
## data:  Before and After
## t = -23.285, df = 149, p-value < 2.2e-16
## alternative hypothesis: true mean difference is not equal to 0
## 95 percent confidence interval:
##  -10.313424  -8.699909
## sample estimates:
## mean difference 
##       -9.506667

Test is statistically significant p < .001

EFFECT SIZE:

library(effectsize)
cohens_d(Before, After, paired = TRUE)

## For paired samples, 'repeated_measures_d()' provides more options.

## Cohen's d |         95% CI
## --------------------------
## -1.90     | [-2.17, -1.63]

REPORT PARAGRAPH

An Dependent T-test was conducted to compare the difference in communication skill of employees before and after attend the professional communication training

Among 150 employees, the results show that PostTraining communicate scores (M = 69.24, SD = 9.48) were significantly higher

than PreTraining scores (M = 59.73, SD = 7.97), t(149) = -23.29, p < .001. The effect size was large, Cohen’s d = -1.90, indicating

a large effect. These results suggest that the communication skill of employees had significant improve after attend communication training