Some data have a distribution that is symmetric and bell-shaped, a mean value of 5.5. We know that 95% of the data is between 4.3 and 6.7. Use the 95% rule to find the standard deviation.

The standard deviation σ = 0.6122

Step-by-step explanation:

Explanation:-

Given mean of the Population  = 5.5

we know that 95% of confidence interval of Z-score = 1.96

95% of confidence interval for mean in normal distribution

(μ±Z₀.₉₅σ)

(μ - 1.96σ , μ +1.96σ)

given that 95% of confidence interval between 4.3 and 6.7

μ - 1.96σ = 4.3

5.5 -1.96σ  = 4.3

5.5 - 4.3 = 1.96σ

1.2 = 1.96σ

σ =

The standard deviation σ = 0.6122

x is the total time in minutes for the free response

you are given number of questions as 15 - m and time per item as 8 minutes

to find x multiply the two givens together:

x = 8 * (15-m) = 8(15-m)

the equation is not included but the answer is (1.50, 2.00, 2.75)

step-by-step explanation: