A fashion designer wants to know how many new dresses women buy each year. Assume a previous study found the variance to be 1.69. She thinks the mean is 7.6 dresses per year. What is the minimum sample size required to ensure that the estimate has an error of at most 0.14 at the 98% level of confidence

Respuesta :

The minimum size of the sample required to ensure that the estimate has an error of at most 0.14 at the 98% level of the confidence interval is 791.

The standard deviation is given as (σ) = 1.69.

The mean number of dresses given (μ) = 7.6.

Margin of error given (M.E.) = 0.14.

Confidence level given = 98%.

Z-Score corresponding to 98% confidence interval (Z) = 2.33.

We are asked to find the minimum size of the sample required to ensure that the estimate has an error of at most 0.14 at the 98% level of the confidence interval.

We assume the size of the sample to be n.

By the formula of Margin of Error:

M.E. = Z*(σ/√n).

Substituting the values, we get:

0.14 = 2.33*(1.69/√n),

or, √n = 2.33*1.69/0.14 = 28.126429,

or, n = 791.096 ≈ 791 (As sample size needs to be a whole number).

Thus, the minimum size of the sample required to ensure that the estimate has an error of at most 0.14 at the 98% level of the confidence interval is 791.

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