Question

Lesson 10.13: Random Sampling and Random Assignment

Check Your Understanding

1. Zach works at the Verizon store and wonders if iPhones last longer if the screen brightness is set to low. He selects a random sample of 20 brand new iPhones from this store and randomly splits them into two groups of 10. For the first group of 10 iPhones, he sets the screen brightness to low and then starts a movie. For the second group of 10 iPhones, he sets the screen brightness to high and then starts a movie. For each iPhone, he measures the amount of time until the battery is all the way dead. He finds that the low brightness iPhones lasted longer, on average, than the high brightness iPhones.

(a) Was this an observational study or an experiment? Explain your reasoning.

(b) What is the explanatory variable and the response variable?

(c) Was a random sample used to collect the data?

(d) Was random assignment used to set up an experiment?

(e) What conclusion can we make from this study?

Answer 1

The answer will be provided below, Your welcome.

Step-by-step explanation: (a) This was an experiment because the screen brightness was intentionally set to low or high for the two groups of iPhones.

(b) The explanatory variable is the screen brightness (low or high) and the response variable is the amount of time until the battery is dead.

(c) Yes, a random sample of 20 iPhones was used.

(d) Yes, random assignment was used to set up the experiment by randomly assigning 10 iPhones to the low brightness group and 10 iPhones to the high brightness group.

(e) We can conclude that there may be a causal relationship between screen brightness and battery life, with low brightness resulting in longer battery life. However, further studies would be needed to confirm this relationship and determine the extent of its effect.