In a survey, 22 people were asked how much they spent on their child's last birthday gift. the results were roughly bell-shaped with a mean of $32 and standard deviation of $17. construct a confidence interval at a 98% confidence level.

Step-by-step explanation:

Tthe population is normally distributed and the sample size is .

Since the population standard deviation is unknown and the sample standard deviation , must replace it, the t distribution must be used for the confidence interval.

Hence with degrees of freedom of 21, .(Read from the t distribution table)

The 98% confidence interval can be constructed  using the formula:

.

From the question the sample mean is dollars and the sample standard deviation is dollars.

We substitute the values into the formula to get

Therefore, we can be 98% confident that the population mean is between is between 19.22 and 44.78 dollars.

1. 3.4/4

2. 0.8/7

3. 0.5 x 3

4. 0.9 x 6

5. 10.8

6. 2.35

7. 0.567

8. 9.35

9. 0.02

10. 0.06

11. 0.16

12. 0.42

13. 0.63

14. 5.6

15. 8.1

16. 9.9

17. 0.28

18. 0.48

19. 0.27

20. 0.49

21. 0.45

22. 0.72

23. 0.9

24. 0.88

25. 0.75

26. 0.16

27. 0.328

28. 0.495

29. 0.72

30. 1.068