In: Statistics and Probability
The file “RadioShack” contains the number of RadioShack stores located in each of the 50 U.S. states and the District of Columbia, as of December
31, 2013. 65 20 76 53 565 82 68 18 12 309 127 24 28 197 122 68 56 75 81 33 99 115 155 81 47 97 28 33 40 36 156 41 342 139 9 203 59 70 232 20 69 22 88 408 41 16 144 111 36 101 19
a. Find mean, Variance, and Standard deviation
b. What percentage of the 50 states have RadioShack stores within
+/1 standard deviations? Round to a whole numb
c. Compute the covariance (round to whole number)
d.Compute the coefficient of correlation (round to 2 decimal places with a leading zero; e.g., 0.50)
(a)
Following table shows the calculations:
X | (X-mean)^2 | |
65 | 1274.918436 | |
20 | 6513.458436 | |
76 | 610.386436 | |
53 | 2275.862436 | |
565 | 215568.9184 | |
82 | 349.914436 | |
68 | 1069.682436 | |
18 | 6840.282436 | |
12 | 7868.754436 | |
309 | 43386.39044 | |
127 | 691.374436 | |
24 | 5883.810436 | |
28 | 5286.162436 | |
197 | 9272.534436 | |
122 | 453.434436 | |
68 | 1069.682436 | |
56 | 1998.626436 | |
75 | 660.798436 | |
81 | 388.326436 | |
33 | 4584.102436 | |
99 | 2.910436 | |
115 | 204.318436 | |
155 | 2947.838436 | |
81 | 388.326436 | |
47 | 2884.334436 | |
97 | 13.734436 | |
28 | 5286.162436 | |
33 | 4584.102436 | |
40 | 3685.218436 | |
36 | 4186.866436 | |
156 | 3057.426436 | |
41 | 3564.806436 | |
342 | 58222.79444 | |
139 | 1466.430436 | |
9 | 8409.990436 | |
203 | 10464.06244 | |
59 | 1739.390436 | |
70 | 942.858436 | |
232 | 17238.11444 | |
20 | 6513.458436 | |
69 | 1005.270436 | |
22 | 6194.634436 | |
88 | 161.442436 | |
408 | 94429.60244 | |
41 | 3564.806436 | |
16 | 7175.106436 | |
144 | 1874.370436 | |
111 | 105.966436 | |
36 | 4186.866436 | |
101 | 0.086436 | |
19 | 6675.870436 | |
Total | 5136 | 577224.5882 |
(b)
The interval corresponding to 1 SD of mean is
Out of 51 data values, 5 are not in the above interval and 46 are in above interval so required percentage is
46 /51 = 0.902
Hence, the required percentage is 90%.
-----------------
For rest parts we need two variables.