Suppose the mean height in inches of all 9th grade students at one high school is estimated. The population standard deviation is 3 inches. The heights of 6 randomly selected students are 60, 72, 68, 66, 73, and 70.

Calculate the sample mean [tex]\(\bar{x}\)[/tex].

Margin of error at [tex]\(95\%\)[/tex] confidence level [tex]\(=\)[/tex] [tex]\(\square\)[/tex]

[tex]\(95\%\)[/tex] confidence interval [tex]\(= [ \square, \square ]\)[/tex]



Answer :

Sure, let's go through the solution step-by-step:

1. Calculate the Sample Mean:
To find the sample mean, sum the heights and divide by the number of students.

Given heights: 60, 72, 68, 66, 73, 70

[tex]\[ \bar{x} = \frac{60 + 72 + 68 + 66 + 73 + 70}{6} = \frac{409}{6} = 68.16666666666667 \][/tex]

2. Estimate the Margin of Error:
To calculate the margin of error at a 95% confidence level, we need to use the z-score corresponding to the 95% confidence level, which is approximately 1.96. Also required is the population standard deviation (σ), which is given as 3 inches, and the sample size (n), which is 6.

The formula for the margin of error [tex]\(E\)[/tex] is:

[tex]\[ E = z \cdot \frac{\sigma}{\sqrt{n}} \][/tex]

Plug in the values:

[tex]\[ E = 1.96 \cdot \frac{3}{\sqrt{6}} = 1.96 \cdot 1.224744871391589 = 2.4004558381776553 \][/tex]

3. Construct the 95% Confidence Interval:
The confidence interval is calculated as:

[tex]\[ (\bar{x} - E, \bar{x} + E) \][/tex]

So,

[tex]\[ (68.16666666666667 - 2.4004558381776553, 68.16666666666667 + 2.4004558381776553) \][/tex]

Simplifying the bounds:

[tex]\[ (65.76621082848902, 70.56712250484432) \][/tex]

Thus, the detailed steps yield:

- Sample Mean ([tex]\(\bar{x}\)[/tex]): 68.16666666666667
- Margin of Error at 95% Confidence Level: 2.4004558381776553
- 95% Confidence Interval: (65.76621082848902, 70.56712250484432)