An app developer seeks to decide between a green and a blue version of a retail app. The developer releases a beta version of the app, and a user who downloads the app is randomly given the green or the blue version. A week after the download, the average time spent on the retail app by the 105 individuals who downloaded the green version and the 103 individuals who downloaded the blue version were, respectively, 14 minutes (SD = 3.3 minutes) and 11 minutes (SD = 3.1 minutes).

An app developer seeks to decide between a green and a blue version of a retail app. The developer releases a beta version of the app, and a user who downloads the app is randomly given the green or the blue version. A week after the download, the average time spent on the retail app by the 105 individuals who downloaded the green version and the 103 individuals who downloaded the blue version were, respectively, 14 minutes (SD = 3.3 minutes) and 11 minutes (SD = 3.1 minutes). What is a 80% confidence interval for the difference between the average time spent by users on the green version of the app and the average time spent by users on the blue version of the app? [ Select] Assume O green # blue. [ Select ] (2.5561, 3.4439) (2.6383, 3.3617) (2.4274, 3.5726) Consider the following interpretations of this 80% confidence interval: ( 2.6248, 3.3751) (a) We can be 80% confident that the difference between the average time spent by users on the green and on the blue version of the app, in the population, is within the interval obtained. (b) We can be 80% confident that the difference between the average time spent by users on the green and on the blue version of the app, in the sample, is within the interval obtained. (c) There is a .80 probability that the difference between the average time spent by users on the green and on the blue version of the app, in the sample, lies in the interval obtained. (d) There is a .80 probability that the difference between the average time spent by users on the green and on the blue version of the app, in the population, lies in the interval obtained. Which of them is correct? [ Select ] ( C ) The 80% confidence interval included only positive values. Can we be sure that the 99% confidence interval also includes only positive values? | [ Select] No, the confidence interval can only include positive values. Yes. The 99% confidence interval will be narrower that the 80% interval, and so it cannot extend to include also negative values. We cannot be sure without computing it. The 99% confidence interval will be wider than the 80% interval, and so it may, in principle, extend so much as to also include negative values. That the population of users of the app includes less than 1000 users. What is an implicit assumption that this analysis needs to rely on That if we repeat the same experiment we will obtain the same group averages. That the first users to download the beta version of the app can be regarded as a random sample from the population That the population averages are equal to the sample averages. Considering the way that this analysis was carried out, which of the following should be said about the population to which the findings can generalize? [ Select ] (a) The population is all individuals who buy the type of products sold on the retail app. (b) The population is all individuals with a smartphone. (c) We should be careful to extend the findings to all potential users of this retail app, because the sample only included individuals who voluntarily downloaded the beta version of the app