Question

2. the average battery life of 2400 manufactured cell phones is recorded

Answer 1

A Z-score helps us to understand how far is the data from the mean. The number of phones who have battery life in the range of 11.4 to 13 range is 1145.

What is Z-score?

A Z-score helps us to understand how far is the data from the mean. It is a measure of how many times the data is above or below the mean. It is given by the formula,

$Z = \dfrac{X- \mu}{\sigma}$

Where Z is the Z-score,

X is the data point,

μ is the mean and σ is the standard variable.

The percentage of phones who have battery life in the range of 11.4 to 13 range is,

$P(11.4 < X < 13) = P(Z < \dfrac{13-13}{0.8}) - P(Z < \dfrac{11.4-13}{0.8})$

                            = 0.50 - 0.0228

                            = 0.4772

Now, the number of phones who have battery life in the range of 11.4 to 13 range is,

Number of phones = 0.4772 × 2400 = 1145.28 ≈ 1145

Hence, the number of phones who have battery life in the range of 11.4 to 13 range is 1145.

Learn more about Z-score:

brainly.com/question/13299273

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