Question

The office of student services at a large western state university maintains information on the study habits of its full-time students. their studies indicate that the mean amount of time undergraduate students study per week is 20 hours. the hours studied follows the normal distribution with a standard deviation of six hours. suppose we select a random sample of 144 current students. what is the probability that the mean of this sample is less than 19.25 hours? g

Answer 1

A suitable probability calculator can tell you the probability is about 6.7%.

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The standard deviation of the distribution of sample means is the population standard deviation (6) divided by the square root of the sample size (√144=12). Thus, your threshold is about (19.25-20)/(6/12) = -1.5 standard deviations from the mean.