Question

Studen Age

28

27

28

30

29

29

35

29

34

29

25

30

28

31

27

27

34

30

26

27

31

32

34

27

31

34

32

29

25

30

32

28

34

28

23

27

30

26

35

31

25

33

29

31

26

33

33

31

38

22

1. Follow a good modeling scheme. Make sure all calculations are done in Excel
2. Cell with formulas, intermediate calculations painted light green
3. All calculations or numbers must have labels or explanations.
4. Final answers should be painted orange
Question: Construct a 70% confidence interval for the mean student age. Interpret the result.

Answer 1

Solution:

Confidence interval for Population mean is given as below:

Confidence interval = Xbar ± t*S/sqrt(n)

From given data, we have

Xbar = 29.66

S = 3.347920463

n = 50

df = n – 1 = 49

Confidence level = 70%

Critical t value = 1.0475

(by using excel)

Confidence interval = Xbar ± t*S/sqrt(n)

Confidence interval = 29.66 ± 1.0475*3.347920463/sqrt(50)

Confidence interval = 29.66 ± 1.0475*0.473467452

Confidence interval = 29.66 ± 0.4960

Lower limit = 29.66 - 0.4960 = 29.1640

Upper limit = 29.66 + 0.4960 = 30.1560

We are 70% confident that the mean age of the students will lies between 29.1640 and 30.1560 years.