Below represent scores on an exam, each entry one score for one student
40 |
99 |
59 |
98 |
63 |
63 |
64 |
65 |
67 |
35 |
67 |
67 |
68 |
70 |
71 |
71 |
71 |
46 |
72 |
72 |
60 |
73 |
74 |
74 |
74 |
75 |
97 |
75 |
62 |
76 |
76 |
76 |
76 |
76 |
77 |
57 |
77 |
98 |
77 |
63 |
78 |
78 |
78 |
79 |
79 |
80 |
80 |
80 |
80 |
80 |
81 |
81 |
92 |
81 |
93 |
82 |
82 |
83 |
83 |
83 |
83 |
83 |
83 |
83 |
84 |
84 |
84 |
84 |
84 |
85 |
85 |
86 |
86 |
86 |
86 |
86 |
87 |
88 |
88 |
77 |
88 |
52 |
89 |
89 |
86 |
84 |
91 |
90 |
92 |
88 |
93 |
93 |
46 |
93 |
94 |
94 |
94 |
61 |
95 |
96 |
55 |
43 |
44 |
50 |
71 |
77 |
72 |
43 |
44 |
By calculation using excel formula average and stddev
mean = 76.6330
S.D. = 14.2111
P(75.0 < x < 85.0)=?
This implies that
P(75.0 < x < 85.0) = P(-0.1149 < z < 0.5888) = P(Z < 0.5888) - P(Z < -0.1149)
P(75.0 < x < 85.0) = 0.7220022770715641 - 0.45426219254773315
P(75.0 < x < 85.0) = {0.2677} . By calculation
n = 109
values between 75 to 85 = 38
P(75.0 < x < 85.0) = 0.2569 by actual data
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