
Concept explainers
Although tables of binomial probabilities can be found in most libraries, such tables are often inadequate. Either the value of p(the
Applications
The following percentages were obtained over many years of observation by the U.S. Weather Bureau. All data listed are for the month of December.
Location | Long-Term Mean % of Clear Days in Dec |
Juneau, Alaska | 18% |
Seattle. Washington | 24% |
Hilo. Hawaii | 36% |
Honolulu, Hawaii | 60% |
Las Vegas, Nevada | 75% |
Phoenix, Arizona | 77% |
Adapted from Local Climatological Data, U.S. Weather Bureau publication, 'Normals, Means, and Extremes' Table.
In the locations listed, the month of December is a relatively stable month with respect to weather. Since weather patterns from one day to the next are more or less the same, it is reasonable to use a binomial probability model.
Let r be the number of clear days in December. Since December has 31 days. 0≤r≤31. Using appropriate computer software or calculators available to you. find the probability P(r) for each of the listed locations when r = 0, 1, 2…., 31.

The probabilities of r=0,1,2,⋯,31 for each of the locations.
Answer to Problem 1UTA
Solution: The probabilities for different cities are tabulated below:
Location | P(r), r=0,1,2,…,30,31 |
Juneau, Alaska | 0.0021, 0.0145, 0.0477,…0,0. |
Seattle, Washington | 0.0002,0.002.0.0094,…,0,0. |
Hilo, Hawaii | 0.00,0.00,0.0001,…0,0. |
Honolulu, Hawaii | 0,0,0,…0,0. |
Las Vegas, Nevada | 0,0,0,…,0.0014,0.0001 |
Phoenix, Arizona | 0,0,0,…,0.0028,0.0003 |
Explanation of Solution
Given: A table consisting of the long-term mean percentage of clear days in December for the different locations has been provided.
Calculation: Consider that r represents a random variable that is defined as the number of clear days. Since December has 31 days, n=31.
The location, Juneau, Alaska, has 18% of clear days in December. So, the probability of success in a single trial (p) = 0.18 and n=31.
Follow the steps given below in a TI-83 Plus calculator to obtain the probabilities for the location, Juneau, Alaska, when r=0,1,2,⋯,31.
Step 1:
Press the 2nd button on the TI-83 Plus calculator and then press the DISTR key.
Step 2:
Scroll down to binompdf (n, p, r) and press ENTER.
Step 3:
Enter the values of n, p and r as 31, 0.18 and 0, respectively, and press ENTER.
The value of P(r=0) is approximately 0.0021.
Similarly, the rest of the probabilities for r=1,2,3,⋯,31 can be calculated by following the same steps as above, but changing the value of r.
Thus, the required probabilities are 0.0021, 0.0145, 0.0477,0.1012, 0.1556,…,0.000.
r | P(r) |
0 | 0.0021 |
1 | 0.0145 |
2 | 0.0477 |
3 | 0.1012 |
4 | 0.1556 |
5 | 0.1844 |
6 | 0.1754 |
7 | 0.1375 |
8 | 0.0906 |
9 | 0.0508 |
10 | 0.0245 |
11 | 0.0103 |
12 | 0.0038 |
13 | 0.0012 |
14 | 0.0003 |
15 | 0.0001 |
16 | 0.00 |
17 | 0.00 |
18 | 0.00 |
19 | 0.00 |
20 | 0.00 |
21 | 0.00 |
22 | 0.00 |
23 | 0.00 |
24 | 0.00 |
25 | 0.00 |
26 | 0.00 |
27 | 0.00 |
28 | 0.00 |
29 | 0.00 |
30 | 0.00 |
31 | 0.00 |
The location, Seattle, Washington, has 24% of clear days in December. So, the probability of success in a single trial (p) = 0.24 and n=31.
Follow the steps given below in a TI-83 Plus calculator to obtain the probabilities for the location, Seattle, Washington, when r=0,1,2,⋯,31.
Step 1:
Press the 2nd button on the TI-83 Plus calculator and then press the DISTR key.
Step 2:
Scroll down to binompdf (n, p, r) and press ENTER.
Step 3:
Enter the values of n, p and r as 31, 0.24 and 0, respectively, and press ENTER.
The value of P(r=0) is approximately 0.0002.
Similarly, the rest of the probabilities for r=1,2,3,⋯,31 can be calculated by following the same steps as above, but changing the value of r.
The required probabilities are:
r | P(r) |
0 | 0.002 |
1 | 0.002 |
2 | 0.0094 |
3 | 0.0286 |
4 | 0.0632 |
5 | 0.1078 |
6 | 0.1475 |
7 | 0.1663 |
8 | 0.1575 |
9 | 0.1271 |
10 | 0.0883 |
11 | 0.0533 |
12 | 0.028 |
13 | 0.0129 |
14 | 0.0053 |
15 | 0.0019 |
16 | 0.0006 |
17 | 0.0002 |
18 | 0.00 |
19 | 0.00 |
20 | 0.00 |
21 | 0.00 |
22 | 0.00 |
23 | 0.00 |
24 | 0.00 |
25 | 0.00 |
26 | 0.00 |
27 | 0.00 |
28 | 0.00 |
29 | 0.00 |
30 | 0.00 |
31 | 0.00 |
The location, Hilo, Hawaii, has 36% of clear days in December. So, the probability of success in a single trial (p) = 0.36 and n=31.
Follow the steps given below in a TI-83 Plus calculator to obtain the probabilities for the location, Hilo, Hawaii, when r=0,1,2,⋯,31.
Step 1:
Press the 2nd button on the TI-83 Plus calculator and then press the DISTR key.
Step 2:
Scroll down to binompdf (n, p, r) and press ENTER.
Step 3:
Enter the values of n, p and r as 31, 0.36 and 0, respectively, and press ENTER.
The value of P(r=0) is approximately 0.0000.
Similarly, the rest of the probabilities for r=1,2,3,⋯,31 can be calculated by following the same steps as above, but changing the value of r.
The required probabilities are:
r | P(r) |
0 | 0.00 |
1 | 0.00 |
2 | 0.0001 |
3 | 0.0008 |
4 | 0.0031 |
5 | 0.0094 |
6 | 0.0229 |
7 | 0.046 |
8 | 0.0775 |
9 | 0.1115 |
10 | 0.1379 |
11 | 0.1481 |
12 | 0.1389 |
13 | 0.1142 |
14 | 0.0826 |
15 | 0.0526 |
16 | 0.0296 |
17 | 0.0147 |
18 | 0.0064 |
19 | 0.0025 |
20 | 0.008 |
21 | 0.0002 |
22 | 0.0001 |
23 | 0.00 |
24 | 0.00 |
25 | 0.00 |
26 | 0.00 |
27 | 0.00 |
28 | 0.00 |
29 | 0.00 |
30 | 0.00 |
31 | 0.00 |
The location, Honolulu, Hawaii, has 60% of clear days in December. So, the probability of success in a single trial (p) = 0.60 and n=31.
Follow the steps given below in a TI-83 Plus calculator to obtain the probabilities for the location, Honolulu, Hawaii, when r=0,1,2,⋯,31.
Step 1:
Press the 2nd button on the TI-83 Plus calculator and then press the DISTR key.
Step 2:
Scroll down to binompdf (n, p, r) and press ENTER.
Step 3:
Enter the values of n, p and r as 31, 0.60 and 0, respectively, and press ENTER.
The value of P(r=0) is approximately 0.0000.
Similarly, the rest of the probabilities for r=1,2,3,⋯,31 can be calculated by following the same steps as above, but changing the value of r.
The required probabilities are:
r | P(r) |
0 | 0.00 |
1 | 0.00 |
2 | 0.00 |
3 | 0.00 |
4 | 0.00 |
5 | 0.00 |
6 | 0.00 |
7 | 0.00 |
8 | 0.001 |
9 | 0.0004 |
10 | 0.0012 |
11 | 0.0034 |
12 | 0.0084 |
13 | 0.0185 |
14 | 0.0357 |
15 | 0.0607 |
16 | 0.091 |
17 | 0.1205 |
18 | 0.1406 |
19 | 0.1443 |
20 | 0.1298 |
21 | 0.102 |
22 | 0.0696 |
23 | 0.0408 |
24 | 0.0204 |
25 | 0.0086 |
26 | 0.003 |
27 | 0.0008 |
28 | 0.0002 |
29 | 0.00 |
30 | 0.00 |
31 | 0.00 |
The location, Las Vegas, Nevada, has 75% of clear days in December. So, the probability of success in a single trial (p) = 0.75 and n=31.
Follow the steps given below in a TI-83 Plus calculator to obtain the probabilities for the location, Las Vegas, Nevada, when r=0,1,2,⋯,31.
Step 1:
Press the 2nd button on the TI-83 Plus calculator and then press the DISTR key.
Step 2:
Scroll down to binompdf (n, p, r) and press ENTER.
Step 3:
Enter the values of n, p and r as 31, 0.75 and 0, respectively, and press ENTER.
The value of P(r=0) is approximately 0.0000.
Similarly, the rest of the probabilities for r=1,2,3,⋯,31 can be calculated by following the same steps as above, but changing the value of r.
The required probabilities are:
r | P(r) |
0 | 0.00 |
1 | 0.00 |
2 | 0.00 |
3 | 0.00 |
4 | 0.00 |
5 | 0.00 |
6 | 0.00 |
7 | 0.00 |
8 | 0.00 |
9 | 0.00 |
10 | 0.00 |
11 | 0.00 |
12 | 0.00 |
13 | 0.0001 |
14 | 0.0003 |
15 | 0.0009 |
16 | 0.0028 |
17 | 0.0074 |
18 | 0.0173 |
19 | 0.0356 |
20 | 0.064 |
21 | 0.1006 |
22 | 0.1372 |
23 | 0.161 |
24 | 0.161 |
25 | 0.1353 |
26 | 0.0937 |
27 | 0.052 |
28 | 0.0223 |
29 | 0.0069 |
30 | 0.0014 |
31 | 0.0001 |
The location, Phoenix, Arizona, has 77% of clear days in December. So, the probability of success in a single trial (p) = 0.77 and n=31.
Follow the steps given below in a TI-83 Plus calculator to obtain the probabilities for the location, Phoenix, Arizona, when r=0,1,2,⋯,31.
Step 1:
Press the 2nd button on the TI-83 Plus calculator and then press the DISTR key.
Step 2:
Scroll down to binompdf (n, p, r) and press ENTER.
Step 3:
Enter the values of n, p and r as 31, 0.77 and 0, respectively, and press ENTER.
The value of P(r=0) is approximately 0.0000.
Similarly, the rest of the probabilities for r=1,2,3,⋯,31 can be calculated by following the same steps as above, but changing the value of r.
The required probabilities are:
r | P(r) |
0 | 0.00 |
1 | 0.00 |
2 | 0.00 |
3 | 0.00 |
4 | 0.00 |
5 | 0.00 |
6 | 0.00 |
7 | 0.00 |
8 | 0.00 |
9 | 0.00 |
10 | 0.00 |
11 | 0.00 |
12 | 0.00 |
13 | 0.00 |
14 | 0.0001 |
15 | 0.0004 |
16 | 0.0012 |
17 | 0.0036 |
18 | 0.0094 |
19 | 0.0216 |
20 | 0.0433 |
21 | 0.0759 |
22 | 0.1156 |
23 | 0.1514 |
24 | 0.1689 |
25 | 0.1584 |
26 | 0.1224 |
27 | 0.0759 |
28 | 0.0363 |
29 | 0.0126 |
30 | 0.0028 |
31 | 0.0003 |
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Chapter 6 Solutions
UNDERSTANDING BASIC STATISTICS (LOOSE)
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