Question

The Federal Pell Grant Program gives grants to low-income undergraduate students. According to the National Postsecondary Student Aid Study conducted by the U.S. Department of Education in 2008, the average Pell grant award for 2007-2008 was $2,600. We wonder if the mean amount is different this year for Pell grant recipients at San Jose State University. Suppose that we randomly select 50 Pell grant recipients from San Jose State University. For these 50 students, the mean Pell grant award is $2,450 with a standard deviation of $600. Let μ = the mean amount of Pell grant awards received by San Jose State University Pell grant recipients this year. We test the following hypotheses. The sample size is greater than 30, so a t-model is a good fit for the sampling distribution. Use this information to answer the next two questions.

a. What is the t-test statistic? If necessary, round to two decimal places.
b. What is the P-value?

Answer 1

a. To find the t-test statistic, we first need to calculate the standard error of the mean using the formula: standard deviation / square root of sample size. In this case, the standard error of the mean is 600 / square root of 50, which is approximately 84.85.

Then, we can calculate the t-test statistic using the formula: (sample mean - hypothesized population mean) / standard error of the mean. In this case, the t-test statistic is (2450 - 2600) / 84.85, which is approximately -1.77.

b. To find the P-value, we need to consult a t-distribution table or use statistical software. Using a two-tailed t-test with 49 degrees of freedom (50-1), we find that the P-value associated with a t-test statistic of -1.77 is approximately 0.084. Therefore, there is a 8.4% chance of obtaining a sample mean of $2,450 or less if the true mean amount of Pell grant awards received by San Jose State University Pell grant recipients this year is actually $2,600.

Note: A common threshold for statistical significance is a P-value of less than 0.05. Since the P-value in this case is greater than 0.05, we cannot reject the null hypothesis and conclude that there is sufficient evidence to support the claim that the mean amount of Pell grant awards received by San Jose State University Pell grant recipients this year is different from $2,600.
a. To find the t-test statistic, we will use the following formula:

t = (sample mean - population mean) / (sample standard deviation / sqrt(sample size))

Here, sample mean = $2,450, population mean = $2,600, sample standard deviation = $600, and sample size = 50.

t = ($2,450 - $2,600) / ($600 / sqrt(50))
t = (-$150) / ($600 / 7.071)
t = (-$150) / $84.85
t ≈ -1.77

The t-test statistic is approximately -1.77.

b. To find the P-value, we need to use a t-distribution table or software to determine the probability of obtaining a t-test statistic as extreme or more extreme than our calculated value. We are doing a two-tailed test, so we need to find the area in both tails.

Looking up the t-test statistic -1.77 in a t-distribution table with 49 degrees of freedom (sample size - 1), we find the P-value is between 0.05 and 0.10. For a more accurate P-value, use software or an online calculator.

So, the P-value is between 0.05 and 0.10.