Questions: A soft drink manufacturer wishes to know how many soft drinks adults drink each week. They want to construct a 95% confidence interval for the mean and are assuming that the population standard deviation for the number of soft drinks consumed each week is 1.1. The study found that for a sample of 949 adults the mean number of soft drinks consumed per week is 3.6. Construct the desired confidence interval. Round your answers to one decimal place.
Lower endpoint: Upper endpoint
Transcript text: A soft drink manufacturer wishes to know how many soft drinks adults drink each week. They want to construct a $95 \%$ confidence interval for the mean and are assuming that the population standard deviation for the number of soft drinks consumed each week is 1.1. The study found that for a sample of 949 adults the mean number of soft drinks consumed per week is 3.6. Construct the desired confidence interval. Round your answers to one decimat place.
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Lower endpoint: $\square$ Upper endpoint $\square$
Solution
Solution Steps
Step 1: Calculate the Z-Score
For a \(95\%\) confidence level, the Z-score is given by:
\[
Z = 1.96
\]
Step 2: Calculate the Margin of Error
The margin of error (\(E\)) is calculated using the formula:
\[
E = Z \times \frac{\sigma}{\sqrt{n}}
\]
Substituting the known values:
\[
E = 1.96 \times \frac{1.1}{\sqrt{949}} \approx 0.07
\]
Thus, the margin of error is:
\[
\text{Margin of Error} = 0.07
\]
Step 3: Construct the Confidence Interval
The confidence interval for the mean is given by:
\[
\bar{x} \pm E
\]
Substituting the sample mean and the margin of error:
\[
3.6 \pm 0.07
\]
This results in the confidence interval:
\[
(3.6 - 0.07, 3.6 + 0.07) = (3.53, 3.67)
\]
Rounding to one decimal place, we have:
\[
(3.5, 3.7)
\]
Final Answer
The lower endpoint is \(3.5\) and the upper endpoint is \(3.7\). Thus, the final answer is:
\[
\boxed{\text{Lower endpoint: } 3.5, \text{ Upper endpoint: } 3.7}
\]