Math Problem Statement

You wish to test the following claim ( H a ) at a significance level of α

0.001 . For the context of this problem, μ d

μ 2 − μ 1 where the first data set represents a pre-test and the second data set represents a post-test.

H o : μ d

0

H a : μ d

0

You believe the population of difference scores is normally distributed, but you do not know the standard deviation. You obtain the following sample of data: pre-test post-test 53.6 66.4 51.8 58.9 57.7 60.4 56.2 58.6 55.4 57.5 59.1 60.8 56.4 52.1 49.6 50.1 51.8 55 62 71.9 45.7 50 60.7 72.5 72.6 63.3 46.4 53.5 46 51.5 50.3 53.7 72.6 66.4 49.3 50.3

What is the test statistic for this sample? test statistic = -1.2204 Incorrect (Report answer accurate to 4 decimal places.)

What is the p-value for this sample? p-value = (Report answer accurate to 4 decimal places.)

Solution

This problem is asking for a paired-sample tt-test, as we are comparing two related sets of data (pre-test and post-test). Here's how to go about solving the problem step by step:

Step 1: State the Hypotheses

  • Null Hypothesis H0H_0: μd=0\mu_d = 0 (there is no difference between the pre-test and post-test scores).
  • Alternative Hypothesis HaH_a: μd>0\mu_d > 0 (the post-test scores are higher than the pre-test scores).

Step 2: Calculate the Differences

For each pair, compute the difference between the post-test and pre-test scores:

di=post-testpre-testd_i = \text{post-test} - \text{pre-test}

Let's compute these differences:

Pre-testPost-testDifference did_i
53.666.412.8
51.858.97.1
57.760.42.7
56.258.62.4
55.457.52.1
59.160.81.7
56.452.1-4.3
49.650.10.5
51.855.03.2
62.071.99.9
45.750.04.3
60.772.511.8
72.663.3-9.3
46.453.57.1
46.051.55.5
50.353.73.4
72.666.4-6.2
49.350.31.0

Step 3: Calculate the Mean and Standard Deviation of the Differences

Let’s denote the differences by did_i. Now we calculate the sample mean of the differences dˉ\bar{d} and the sample standard deviation sds_d.

dˉ=1ni=1ndi\bar{d} = \frac{1}{n} \sum_{i=1}^{n} d_i

sd=1n1i=1n(didˉ)2s_d = \sqrt{\frac{1}{n-1} \sum_{i=1}^{n} (d_i - \bar{d})^2}

Where:

  • nn is the number of pairs.
  • did_i is the difference for each pair.

Step 4: Calculate the Test Statistic

The test statistic for a paired tt-test is given by:

t=dˉsd/nt = \frac{\bar{d}}{s_d / \sqrt{n}}

Where:

  • dˉ\bar{d} is the mean of the differences.
  • sds_d is the standard deviation of the differences.
  • nn is the number of data pairs.

Step 5: Find the p-value

After calculating the test statistic, you can find the p-value using the t-distribution with n1n-1 degrees of freedom. This is a one-tailed test because the alternative hypothesis is μd>0\mu_d > 0.


I'll calculate these steps for you now.The test statistic for the sample is t=2.2771t = 2.2771.

The corresponding p-value is p=0.0180p = 0.0180 (accurate to four decimal places).

Since the p-value 0.01800.0180 is greater than the significance level α=0.001\alpha = 0.001, we do not reject the null hypothesis H0H_0. There isn't enough evidence at the 0.001 significance level to conclude that the post-test scores are significantly greater than the pre-test scores.

Would you like to ask any questions or need further clarification on the process?

Here are 5 related questions to expand the topic:

  1. How does the sample size affect the outcome of a t-test?
  2. What is the difference between one-tailed and two-tailed hypothesis tests?
  3. Why do we use the t-distribution instead of the normal distribution in this case?
  4. How can we interpret the p-value in the context of hypothesis testing?
  5. What are the assumptions behind using a paired t-test?

Tip: Always check the assumptions of normality and paired structure before applying a paired-sample t-test to ensure valid results.

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Math Problem Analysis

Mathematical Concepts

Paired t-test
Hypothesis testing
Normal distribution

Formulas

Mean of differences: \bar{d} = \frac{1}{n} \sum_{i=1}^{n} d_i
Standard deviation of differences: s_d = \sqrt{\frac{1}{n-1} \sum_{i=1}^{n} (d_i - \bar{d})^2}
t-statistic for paired t-test: t = \frac{\bar{d}}{s_d / \sqrt{n}}

Theorems

Central Limit Theorem
Student's t-distribution

Suitable Grade Level

Undergraduate (Statistics/Introductory Hypothesis Testing)