Students obtained a mean score of 400 and standard deviation of 40 in a test with a bell-shaped distribution. What approximate percentage of the students above 520

0.00135

Step-by-step explanation:

Given that :

Mean, μ = 400

Standard deviation, σ = 40

Approximate percentage of students above 520 ;

Using the relation :

Z = (x - mean) / standard deviation

P(x > 520)

Zscore = (520 - 400) / 40

Zscore = 120 / 40

Z = 3

P(Z > 3) = 1 - P(Z < 3)

P(Z < 3) = 0.99865 (Z probability calculator)

1 - 0.99865 = 0.00135

The variance of the given sample is 7.3

Hence the option A. 7.3 is correct

Step-by-step explanation:

The formula of Variance is:

x                                  

10                                           4

15                                           9

8                                           16

16                                          16

14                                           4

12                                           0

9                                             9

12                                            0

14                                            4

10                                            4

Therefore, the variance is: