Question

2. The following are data for thickness (in cm) of tree bark, obtained from a SRS. Let's assume 1.3 cm for the population. that σ 3.0 3.2 1.7 0.3 2.4 2.6 2.7 1.5 2.0 3.1 0.2 2.2 3.6 3.2 4.0 1.3 3.2 2.3 2.7 1.4 1.6 (a) (4 points) Make a histogram of the data. Is there evidence against the conjecture that the data comes from a Normal distribution? (b) (4 points) Construct a 96% confidence interval for the mean thickness of tree bark. (c) (4 points) What sample size would be necessary to guarantee a margin of error of less than 0.3 cm for our 96% confidence interval?

Answer 1

A)

From the given data:

0.2
0.3
1.3
1.4
1.5
1.6
1.7
2
2.2
2.3
2.4
2.6
2.7
2.7
3
3.1
3.2
3.2
3.2
3.6
4

Histogram:

Frequency Table Class Count 0-0.8 1.4-2 2.1-2.7 2.8-3.4 3.5-4.1 Your Histogram Mean Standard Deviation (s) Skewness Kurtosis Lowest Score Highest Score Distnibution Range Total Number of Score3 Number of Distinct Scores Lowest Class Value Highest Class Value Number of Clas3e3 Class Range 2.29524 1.0092 0.51024 0.14922 0.2 3.8 21 18 0.7

2.1 Histogram (Frequency Diagram) 2.8 3.5 0.7 4.2 1.4

Mean=2.295

Mode=3.2

and Median=2.4

From the above histogram we can see there is no outliers and can said to be approximately normal.

千8.2 - 2.293 population mam, Shandor? diva5㎝ (6)-13 2.235 t 2.074 X 2.293 + 0.5&3 ente): 0.3 He rene hare mardin Ow, 2.054x 1.3 0.3 9.22 18 67