Suppose that a restaurant chain claims that its bottles of ketchup contain 24 ounces of ketchup on average, with a standard deviation of 0.4 ounces. If you took a sample of 49 bottles of ketchup, what would be the approximate [tex]$95 \%$[/tex] confidence interval for the mean number of ounces of ketchup per bottle in the sample?

A. [tex]$24 \pm 0.229$[/tex]
B. [tex]$24 \pm 0.029$[/tex]
C. [tex]$24 \pm 0.057$[/tex]
D. [tex]$24 \pm 0.114$[/tex]



Answer :

To determine the 95% confidence interval for the mean number of ounces of ketchup per bottle in the given sample, we follow these steps:

1. Identify the given information:
- Population mean ([tex]\(\mu\)[/tex]) = 24 ounces
- Population standard deviation ([tex]\(\sigma\)[/tex]) = 0.4 ounces
- Sample size ([tex]\(n\)[/tex]) = 49 bottles
- Confidence level = 95%

2. Calculate the standard error of the mean (SE):
The standard error is calculated using the formula:
[tex]\[ \mathrm{SE} = \frac{\sigma}{\sqrt{n}} \][/tex]
Substituting the given values:
[tex]\[ \mathrm{SE} = \frac{0.4}{\sqrt{49}} = \frac{0.4}{7} = 0.0571 \][/tex]

3. Determine the z-score for the 95% confidence level:
For a 95% confidence interval, the z-score (critical value) is approximately 1.96.

4. Calculate the margin of error (ME):
The margin of error is given by:
[tex]\[ \mathrm{ME} = z \times \mathrm{SE} \][/tex]
Substituting the values:
[tex]\[ \mathrm{ME} = 1.96 \times 0.0571 \approx 0.112 \][/tex]

5. Construct the confidence interval:
The confidence interval is calculated as:
[tex]\[ \text{Confidence Interval} = \mu \pm \mathrm{ME} \][/tex]
Substituting the values:
[tex]\[ \text{Confidence Interval} = 24 \pm 0.112 \][/tex]

This approximate margin of error corresponds to one of the provided choices:

- A. [tex]\(24 \pm 0.229\)[/tex]
- B. [tex]\(24 \pm 0.029\)[/tex]
- C. [tex]\(24 \pm 0.057\)[/tex]
- D. [tex]\(24 \pm 0.114\)[/tex]

Given our computed margin of error of approximately 0.112, the closest match among the choices is:

D. [tex]\(24 \pm 0.114\)[/tex]

Therefore, the correct answer is:

D. [tex]\(24 \pm 0.114\)[/tex]

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