Facebook advertisement. Facebook has numerous advertisement-targeting options for discovery and the performance differs for each client. As a result, there are now over 2 million advertisers who have decided to start advertising on Facebook. A researcher is interested in estimating the average click-through rate or CTR (in %) on Facebook

(i.e., the percentage of people who have actually clicked on an advertisement after seeing it). For his research, he selects 30 days’ CTR and wants to determine if there is a significant difference in the average CTR between the legal advertisers and the retail advertisers. He reveals the descriptive statistics of the CTR on both advertisers as follows:

Advertiser N Mean StDev Min Q1 Med Q3 Max Legal 30 1.61 3.51 1.37 1.41 1.53 1.74 1.82 Retail 30 1.59 1.79 1.22 1.39 1.44 1.63 1.65

a) Write the null and alternative hypotheses.

b) Find the 95% confidence interval for the difference between the mean CTR for the two groups of advertisers.

c) Is there a significant difference between the mean CTR for these two groups? Explain.