preference
Rachel Hunn
12/1/2017
Step 1 Design the experiment
The experiment comes from a test on Example 6 part b that describes whether people prefer certain products if they are primed or not.
Step 2 Collect and load the data
library(ggplot2)
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 1Step 3 Describe the Data
The data has forty two rows and two columns. The columns are preference and primed. There are two groups that have to evaluate a specific label and one group is primed before seeing the product. The other group is not. The researchers want to test their attitudes to the label.
Step 4 Identify the purpose of the study
The purpose of the study is to see whether people prefer a brand more if they are primed before to see a specific label or if they are not primed beforehand. The product has a picture of a dog on the label. The researchers wanted to see whether people who were primed had a higher preference to the product. The primed people were exposed to pictures of animals beforehand and then shown the product. The other group was not primed and the researchers wanted to see if their attitude was lower than the primed group.
Step 5 Visualize data
library(ggplot2)
ggplot(data=preference, mapping=aes(x=as.factor(primed), y=preference)) + geom_point()
Step 6 Interpret the Plot
The preference would be higher for the primed rather than the people not primed. The graph shows that people who are primed have a higher preference to the product with the specific label. Primed people had a higher attitude to the product with the label of a dog than the other people who were not primed beforehand. Those people had a lower attitude toward the product.
Step 7 Null Hypothesis
The null hypothesis is that the means of difference would be zero. This means that the primed and non-primed people would have the same preference. The means would be the same.
Step 8 Alternative Hypothesis
The alternative hypothesis would be that the mean would not be zero. They would be unequal. The primed group would be higher than the other group because they would have a higher preference.
Step 9 Decide on type of test
The test we will use is a T test. We are using a T test because we are trying to find whether or not the means of the two populations are equal. T tests are trying to find the population means of a quantitative variable.
Step10 One or two sample?
We would use a two test sample. One for the primed and the other for preference.
Step 11 Check the assumptions of the test
The graph shows that both were close enough to the line to be determined Normal.
gg <- ggplot(data=preference)
ggplot(data=preference) + geom_qq(mapping=aes(sample=preference, color=as.factor(primed)))
Step 12 Decide on the level of significance
The level of significance will be 0.05.
Step 13 Perform the Test
t.test(formula=preference~as.factor(primed), data=preference)##
## Welch Two Sample t-test
##
## data: preference by as.factor(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 2.972727Step 14 Interpret the p-value
The p value is less than the level of significance. The p value is 0.002666 and the level of signficiance is 0.05. Therefore, we will reject the null hypothesis because the populations means are not zero.
Step 15 Interpret the confidence interval
Since the confidence interval is not zero, they are not different for the difference in means. The farther they are from zero the more different they are. The confidence interval was -1.577912 -0.357543 and the mean estimate for 0 is 2.005000 and 1 is 2.972727.
Step 16 Interpret the sample estimates
We fail to reject the alternative hypothesis and therefore people who are primed to see the product will have a higher preference. The sample estimate guesses that there are 2.972727 on average more preference for the primed group.
Step 17 Conclusion
The primed group has a higher preference to the label with the animal than the group who was not primed. We reject the null hypothesis and accept the alternative hypothesis. More people will prefer a product if they are primed before than if they are not.