A student measuring how gasoline prices change records the cost of gas at 10 ran
ID: 3318795 • Letter: A
Question
A student measuring how gasoline prices change records the cost of gas at 10 randomly selected stations in her hometown. One week later, she records the price again at the same 10 stations. She wants to estimate the mean price increase and subtracts week 2 for week 1 . Her 90% confidence interval is -SO 23 -SO 06 What can she conclude? Choose the correct answer below. 0 A- O B. ° C. It cannot be concluded whether one is higher than the other. These are both negative numbers so the week 2 prices are on average higher than the week 1 prices. These are both negative numbers so the week 2 prices are on average lower than the week 1 prices.Explanation / Answer
Given:
Student wants to calculate increase in mean price. She subtracts Week 2 from week 1
Values for 90% confidence interval are both negative.
This is possible when Week1 average price is less than Week 2 average price
Hence, Option B (week 2 pricees are on average higher than week 1)
Had it been both positive values for confidence interval in that case it would have been option C
and if confidence interval contains one negative and one positive value then option A
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