Question

In a consumer research study, several Meijer and Walmart stores were surveyed at random and the average basket price was recorded for each. It was found that the average basket price for 35 Meijer stores was $49.363 with a standard deviation of $10.631. Similarly, 53 Walmart stores had an average basket price of $59.558 with a standard deviation of $14.543. If a 95% confidence interval for the difference between the true average basket prices of Meijer versus Walmart is calculated, what is the margin of error? You can assume that the standard deviations of the two populations are statistically similar.

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 9 weekdays and finds an average of 220 gallons of milk sold on those days with a standard deviation of 33.256. 9 (total) Saturdays and Sundays are sampled and the average number of gallons sold is 301.26 with a standard deviation of 47.524. Construct a 99% 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.

It is believed that using a solid state drive (SSD) in a computer results in faster boot times when compared to a computer with a traditional hard disk (HDD). You sample a group of computers and use the sample statistics to calculate a 99% confidence interval of (-6.86, 3.16). This interval estimates the difference of (average boot time (HDD) - average boot time (SSD)). What can we conclude from this interval?

Answer 1