Preference

preference <- read.csv("preference.csv")
preference

##    preference primed
## 1         1.8      0
## 2         0.1      0
## 3         4.0      0
## 4         2.1      0
## 5         2.4      0
## 6         3.4      0
## 7         1.7      0
## 8         2.2      0
## 9         1.9      0
## 10        1.9      0
## 11        0.1      0
## 12        3.3      0
## 13        2.1      0
## 14        2.0      0
## 15        1.4      0
## 16        1.6      0
## 17        2.3      0
## 18        1.8      0
## 19        3.2      0
## 20        0.8      0
## 21        1.7      1
## 22        1.7      1
## 23        4.2      1
## 24        3.0      1
## 25        2.9      1
## 26        3.0      1
## 27        4.0      1
## 28        4.1      1
## 29        2.9      1
## 30        2.9      1
## 31        1.2      1
## 32        4.0      1
## 33        3.0      1
## 34        3.9      1
## 35        3.1      1
## 36        2.5      1
## 37        3.2      1
## 38        4.1      1
## 39        3.9      1
## 40        1.1      1
## 41        1.9      1
## 42        3.1      1

Describe Data:

There are two columns and 42 rows in the chart. Each row represents a different person and the preference column represents on a scale of 1 to 6 if the consumer liked it while the primed column represents whether the consumer is exposed to an animal on the label. The primed group is denoted as 1 on the table while the non-primed group is denoted as 0.

Identify the purpose of the study

The purpose of the study is to determine if an animal on a bottle, in this case a dog shampoo bottle, affected how much a consumer liked the product.

Visualize Data

library(ggplot2)
ggplot(data=preference, mapping=aes(x=as.factor(primed), y=preference)) + geom_point()

Interpret the plot

According to the plot, on average, people with non-primed bottles had a preference of 2 while, on average, people with primed bottles has a preference of 3-4. Therefore, people with primed bottles were more satisfied than those with non-primed bottles.

Formulate the null hypothesis

The primed and non-primed groups will have the same mean.

Identify the alternative hypothesis

The primed and non-primed groups will not be equal. The primed mean will be higher than the non-primed group.

Decide on type of test

T-test

Choose one sample or two

Two sample

Check assumptions of the test

ggplot(data=preference) + geom_qq(mapping=aes(sample=preference))

Decide on a level of significance of the test

0.05

Perform the test

t.test(formula=preference~primed, data=preference)

## 
##  Welch Two Sample t-test
## 
## data:  preference by primed
## t = -3.2072, df = 39.282, p-value = 0.002666
## alternative hypothesis: true difference in means is not equal to 0
## 95 percent confidence interval:
##  -1.577912 -0.357543
## sample estimates:
## mean in group 0 mean in group 1 
##        2.005000        2.972727

Interpret the p-value

Since the p-value is less than the level of significance, the null hypothesis is rejected.

Interpret the confidence interval

Confidence interval is a range of values that are plausable for the difference of means. However, zero is not plausable, so the means will not be the same. Therefore, the null-hypothesis is rejected. There is a 95 percent confidence interval between -1.577912 and -0.357543.

Interpret the sample estimates

The mean for group 0 is 2.005000 while the mean for group 1 is 2.972727, so the mean for group 1 is about .9 larger than group 0.

State your conclusion

In conclusion, group 1 had a higher satisfaction number than group 0. Therefore, when someone sees a lable with an animal on it, then they are more likely to buy it because they like the label more.