Question

The distribution of the amount of money spent by students on textbooks in a semester is approximately normal in shape with a mean of 349 and a standard deviation of 24. According to the standard deviation rule, approximately 95% of the students spent between _____$ and _____$ on textbooks in a semester.

Answer 1

$301 - $397

Explanation:

Using the Empirical rule

1) 68% of data falls within 1 standard deviation from the mean - that means between μ - σ and μ + σ .

2)95% of data falls within 2 standard deviations from the mean - between μ – 2σ and μ + 2σ .

3)99.7% of data falls within 3 standard deviations from the mean - between μ - 3σ and μ + 3σ .

From the above question,

Mean = 349 , standard deviation = 24.

Confidence interval = 95%

Using 2)95% of data falls within 2 standard deviations from the mean - between μ – 2σ and μ + 2σ .

μ – 2σ

= 349 - 2(24)

= 349 - 48

= 301

μ + 2σ

349 + 2(24)

= 349 + 48

= 397

Therefore, according to the standard deviation rule, approximately 95% of the students spent between $301 and $397 on textbooks in a semester.