Question 7 (1 point)
The owner of a local supermarket wants to estimate the difference between the average number of gallons of milk sold per day on weekdays and weekends. The owner samples 30 weekdays and finds an average of 216.789 gallons of milk sold on those days with a standard deviation of 38.9547. 30 (total) Saturdays and Sundays are sampled and the average number of gallons sold is 330.011 with a standard deviation of 45.3883. Construct a 95% confidence interval to estimate the difference of (average number of gallons sold on weekdays – average number of gallons sold on weekends). Assume the population standard deviations are the same for both weekdays and weekends.
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Question 8 (1 point)
The owner of a local golf course wants to estimate the difference between the average ages of males and females that play on the golf course. He samples a group of men and women and then uses the sample statistics to calculate a 95% confidence interval of (7.02, 24.01). This interval estimates the difference of (the average age of men – the average age of women). What can we conclude from this interval?
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Question 9 (1 point)
A pharmaceutical company is testing a new drug to increase memorization ability. It takes a sample of individuals and splits them randomly into two groups. After the drug regimen is completed, all members of the study are given a test for memorization ability with higher scores representing a better ability to memorize. You are presented a 95% confidence interval for the difference in population mean scores (with drug – without drug) of (-4.52, 8.21). What can you conclude from this interval?
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Question 10 (1 point)
A restaurant wants to test a new in-store marketing scheme in a small number of stores before rolling it out nationwide. The new ad promotes a premium drink that they want to increase the sales of. 17 locations are chosen at random and the number of drinks sold are recorded for 2 months before the new ad campaign and 2 months after. The average difference in nationwide sales quantity before the ad campaign to after (after – before) is 3.8 with a standard deviation of 8.71. Using this information, they calculate a 95% confidence paired-t interval of (-0.68, 8.28). Which of the following is the best interpretation?
Question 10 options:
We only have the sample means, we need to know the population means in order to calculate a confidence interval.