X Chart and P Chart

1: The mean time to clean a motel room is 15.0 min and the standard deviation is 1.6 min and the data are normally distributed. a. What percentage of the rooms will take less than 12.0 min to complete?
Answer: 0.0301%
Reasoning/Work: from my understanding I subtracted 1.8 from 1.88 which is my answer = .08 then I found the answer on the table b. What percentage of the rooms will take more than 21.0 min to complete?
Answer: 0 %
Reasoning/Work: the answer is 0. c. What percentage of the rooms will take between 12.0 and 20.5 min to complete?
Answer: 0.97%
Reasoning/Work: I found the a of the 2 possibilities then I subtracted the smaller a from the bigger a. 2: In this question you will use the calculations you made for question 7: of Homework 3 to support your judgment concerning the normality of the distribution of the data shown in question 2: (also of Homework 3). Give reasons for your answer which might include calculations and/or graphs.
Answer:
Reasoning/Work:

3: Using normal probability paper, determine (judgment) the normality of the distribution of the following data:
2.566, 2.565, 2.545, 2.551, 2.550, 2.564, 2.542, 2.561, 2.532, 2.565, 2.569, 2.552, 2.558, 2.562, 2.552, 2.575, 2.547, 2.545, 2.559, 2.558, 2.552, 2.563
Use the probability graph paper in "Course Documents". You may print it, then plot the points by hand, then scan it into a Word doc. Or you may drag the blue points at the top of the graph onto the appropriate coordinates on the graph.
Answer:

xi i pp
32
1
2.272727
42
2
6.818182
45
3
11.36364
45
4
15.90909
47
5
20.45455
50
6
25
51
7
29.54545
52
8
34.09091
52
9
38.63636
52
10
43.18182
52
11
47.72727
58
12
52.27273
58
13
56.81818
59
14
61.36364
61
15
65.90909
62
16
70.45455
63
17
75
64
18
79.54545
65
19
84.09091
65
20
88.63636
66
21
93.18182
75
22
97.72727

Reasoning/Work:

4: Data on the amount of water