StatProb Lesson 4 Exercise 7 (SY 24 - 25)

If the sample size is 25, then what is the degrees of freedom?

What is the critical t-value for a 90% confidence level when the degrees of freedom is 24? (3 d. p.)

What is the critical t-value for a 95% confidence level when the sample size is 24? (3 d. p.)

Does the following situation involve a normal distribution, a t-distribution, or neither? In a random sample of 10 adults, the mean waste generated per person per day was 4.50 pounds and the standard deviation was 1.21 pounds. Assume that the random variable is normally distributed.

• normal distribution

• t-distribution

• neither

In a random sample of 10 adults, the mean waste generated per person per day was 4.50 pounds and the standard deviation was 1.21 pounds. Assume that the random variable is normally distributed. What is a point estimate for the population mean waste? Do not label your answer

In a random sample of 10 adults, the mean waste generated per person per day was 4.50 pounds and the standard deviation was 1.21 pounds. Assume that the random variable is normally distributed. Construct a 99% confidence interval for the population mean. Round off margin of error to 1 d.p.

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Does the following situation involve a normal distribution, a t-distribution, or neither? In a random sample of 11 college football players, the mean weekly time spent weightlifting was 7.2 hours. Assume that the population data is normally distributed. From past studies, the population standard deviation was 1.9 hours.

• normal distribution

• t-distribution

• neither

In a random sample of 11 college football players, the mean weekly time spent weightlifting was 7.2 hours. Assume that the population data is normally distributed. From past studies, the population standard deviation was 1.9 hours. What is the margin of error for a 90% confidence interval? (1 d. p.)

In a random sample of 11 college football players, the mean weekly time spent weightlifting was 7.2 hours. Assume that the population data is normally distributed. From past studies, the population standard deviation was 1.9 hours. Interpret the results of the 90% confidence interval for the population mean weekly time spent weightlifting.

• With 90% confidence, we can say that the population mean weekly time spent weightlifting is between 6.3 hours and 8.1 hours.

• With 90% confidence, we can say that the population mean weekly time spent weightlifting is between 6.2 hours and 8.0 hours.

• With 90% confidence, we can say that the population mean weekly time spent weightlifting is between 6.4 hours and 8.2 hours.

• With 90% confidence, we can say that the population mean weekly time spent weightlifting is between 6.2 hours and 8.3 hours.

Does the following situation involve a normal distribution, a t-distribution, or neither? In a random sample of 13 people, the mean length of stay at a hospital was 6.3 days. From past studies, the population standard deviation was 1.7 day. Lengths of stay are not normally distributed.

• normal distribution

• t-distribution

• neither