Statistics : finding critical value
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A survey in 2010 showed that college students study for a statistics exam on average for three hours and ten minutes. To determine if the average time is changed for the statistics exam data gathered from 81 students in a Midwest University. The sample showed that the average studying time for a statistics exam is two hours and fifty minutes with a standard deviation of one hour and thirty minutes. Let .
a. State the null and alternative hypothesis to be tested.
b. Identify the level of significance.
c. Identify the test statistics.
d. Determine the critical value for this test and formulate a decision rule using the critical value.
e. Compute the test statistics.
f. What do you conclude? Interpret the results.
This is a statistics question I need help with finding the lower limit and upper limit.
Finding Critical Values. Find the critical value za/2 that corresponds to the given confidence level. 90%