This is a statistics question:

(A) Select a random sample of 30 student from our population (we have a data entry to get the sample from). At the 0.05 level of significance is there evidence that the average travel time is greater than 45 minutes?

(B) What assumptions must hold in order to perform the test in (A)?

(C) Evaluate the assumption in (B) through a graphical approach. Are the results valid? Discuss.

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Part (A) is the one I need the most help with,but more help is always welcome
I'm not sure which formula to use, am I using the null hypothesis? Z-test? I'm SO confused. What is the procedure for solving this?
THANKS SO MUCH IN ADVANCE FOR ANY HELP!

You'll need to calculate the mean and standard deviation from your data. These values will be needed in the following formula:

t = (sample mean - population mean)/(standard deviation divided by the square root of the sample size)

Note: T-tests can be used for samples sizes 30 or less.

Ho: µ = 45 -->null hypothesis
Ha: µ > 45 -->alternate hypothesis

Calculate your t-test statistic from the formula. Determine the critical value using a t-table. Determine if the test statistic exceeds the critical value.
If it does not, you cannot reject the null hypothesis. If it does, you reject the null and accept the alternate hypothesis.

Assumptions for a t-test are that the data is independently and randomly sampled from the population, and that the data is normally distributed in the population (this is the normality assumption).

I hope this will help.