**Chapter 10, Problem 24-a modified (skip b and c).**

Modify the subquestion (a) as follows: (a) Conduct a two-tail test with alpha = .05 to examine whether the data indicate a significantly higher estimated speed for the “smashed into” group. Make sure to show your work for the following intermediate steps:

- State your hypotheses
- Sketch the sampling distribution. Shade the part that you are interested in.
- Identify your critical values using the t table
- Compute the pooled variance and estimate of standard error. Show your work.
- Compute the t score for your sample mean difference.
- Decide whether you reject or fail to reject the null hypothesis. As your final conclusion, state whether question-wording impacts perceptions of car speed.

**Failing to show these intermediate steps will result in point reductions.**Hint: similar to text pp.277-279 and lecture slides 8-13.

**Estimation, P.265 (within Chapter 9), Problem 18-b (skip a and c)**As shown in the lecture slides, show the following intermediate steps:

- Identify the degree of freedom.
- Sketch the sampling distribution. Shade the part you are interested in. In the sketch, identify what proportion/percentage is assigned in each tail and what proportion/percentage is in the middle part.
- Identify the t score from the t table.
- Compute the sample variance.
- Compute the estimate of standard error.
- Give your point estimate.
- Compute the upper bound and the lower bound of the confidence interval.
**Failing to show these intermediate steps will result in point reductions.**

Also, answer the following question: Did anxiety score increase since 1950s? Explain your answer by using the confidence interval you just calculated.

Hint: Similar to lecture slides 5-14 and textbook pp.253-255.

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