7

The result of throwing two dice 120 times is represented by the table:

Sums 2 3 4 5 6 7 8 9 10 11 12
No. of Times 3 8 9 11 20 19 16 13 11 6 4

1. Calculate the mean and standard deviation.

2. Find the percentage of values in the interval (x − σ, x + σ).


xi fi xi · fi xi2 · fi
2 3 6 12
3 8 24 72
4 9 36 144
5 11 55 275
6 20 120 720
7 19 133 931
8 16 128 1024
9 13 117 1053
10 11 110 1100
11 6 66 726
12 4 48 576
  120 843 6633

1

Statistical Operations

2

x − σ = 4.591 x + σ = 9.459

The values in the interval (4.591, 9.459) are those relating to the amounts of 5, 6, 7, 8 and 9.

11 + 20 + 19 + 16 + 13 = 79

Statistical Operations