Question

The shaded area in the distribution below represents approximately 95% of the data. Use the diagram to find the mean and the standard deviation.

Answer 1

Answer:

mean = 85, standard deviation = 3.5

Step-by-step explanation:

The empirical rule states that for a normal distribution, 68% of the data falls within one standard deviation of the mean, 95% falls within two standard deviation of the mean and 99.7% falls within three standard deviation of the mean.

From the diagram since the shaded are is approximately 95% of the data. Hence 95% falls within two standard deviations of the mean.

σ = standard deviation, μ = mean

Hence; μ ± 2σ = (78, 92)

μ - 2σ = 78       (1);  

μ + 2σ = 92       (2)

Adding equation 1 and 2, gives 2μ = 170

μ = 85

μ - 2σ = 78

85- 2σ = 78

2σ = 7

σ = 3.5