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?

Question 4 which was a foundation of the industrial revolution? a) large states held huge supplies of raw materials. b) coal replaced wood as the primary source of fuel. c) road infrastructure replaced waterways for transport. d) mercantilist policies drove down the price of goods. question 7 which was not a government response to the socialist challenges? a) establishing universal suffrage to all classes b) introducing medical insurance and pensions c) prohibiting underground employment for women d) restricting child labor for children under ten years old question 9 which was a cause of the boer war? a) movement and settlement of bantu peoples into afrikaner-populated states b) independence of northern afrikaner territories from british colonial authority c) evacuation of most afrikaner people out of south africa and back into europe d) british reconstitution of afrikaner-held territories into the union of south africa