Question

The sales data for July and August of a frozen yogurt shop are approximately normal.

The mean daily sales for July was $270 with a standard deviation of $30. On the 15th of July, the shop sold $315 of yogurt.

The mean daily sales for August was $250 with a standard deviation of $25. On the 15th of August, the shop sold $300 of yogurt.

Which month had a higher z-score for sales on the 15th, and what is the value of that z-score?

a.)
August, with a z-score of 1.67.
b.)
July, with a z-score of 1.5.
c.)
July, with a z-score of 1.8.
d.)
August, with a z-score of 2.

Answer 1

Answer: D

Explanation:

To determine which month had a higher z-score for sales on the 15th, we need to calculate the z-scores for each month's sales.

For July:

z-score = (x - μ) / σ

where x is the sales on the 15th, μ is the mean daily sales for July, and σ is the standard deviation of daily sales for July.

Plugging in the values, we get:

z-score for July = (315 - 270) / 30 = 1.5

For August:

z-score = (x - μ) / σ

where x is the sales on the 15th, μ is the mean daily sales for August, and σ is the standard deviation of daily sales for August.

Plugging in the values, we get:

z-score for August = (300 - 250) / 25 = 2

Since the z-score for August is higher than the z-score for July, August had a higher z-score for sales on the 15th.

The value of the z-score for August's sales on the 15th was 2.