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grandymaker [24]
2 years ago
7

A study was conducted to estimate the difference in the mean salaries of elementary school teachers from two neighboring states.

A sample of 10 teachers from the Indiana had a mean salary of $28,900 with a standard deviation of $2300. A sample of 14 teachers from Michigan had a mean salary of $30,300 with a standard deviation of $2100. Determine a 95% confidence interval for the difference between the mean salary in Indiana and Michigan.(Assume population variances are different.)
Mathematics
1 answer:
umka21 [38]2 years ago
6 0

Answer:

(28900-30300) -2.07 \sqrt{\frac{2300^2}{10} +\frac{2100^2}{14}} = -3301.70

(28900-30300) +2.07 \sqrt{\frac{2300^2}{10} +\frac{2100^2}{14}} = 501.698

The confidence interval would be -3301.70 \leq \mu \leq 501.698 and since the confidence interval contains the value of 0 we don't have enough evidence to conclude that the difference between the two states for the salary of teachers are significantly different.

Step-by-step explanation:

We have the following info given by the problem

\bar X_1 = 28900 the sample mean for the salaries of teachers in Indiana

s_1 = 2300 the sample deviation for the salary of  teachers in Indiana

n_1 =10 the sample size from Indiana

\bar X_2 = 30300 the sample mean for the salaries of teachers in Michigan

s_2 = 2100 the sample deviation for the salary of  teachers in Michigan

n_2 =14 the sample size from Michigan

We want to find a confidence interval for the difference in the two means and the formula for this case is given by;

(\bar X_1 -\bar X_2) \pm t_{\alpha/2}\sqrt{\frac{s^2_1}{n_1} +\frac{s^2_2}{n_2}}

The degrees of freedom for this case are:

df = n_1 +n_2 -2= 10+14-2 =22

The confidence is 95%so then the significance is \alpha=0.05 and the \alpha/2 =0.025, we need to find a critical value in the t distribution with 22 degrees of freedom who accumulates 0.025 of the area on each tail and we got:

t_{\alpha/2}= 2.07

And now replacing in the formula for the confidence interval we got:

(28900-30300) -2.07 \sqrt{\frac{2300^2}{10} +\frac{2100^2}{14}} = -3301.70

(28900-30300) +2.07 \sqrt{\frac{2300^2}{10} +\frac{2100^2}{14}} = 501.698

The confidence interval would be -3301.70 \leq \mu \leq 501.698 and since the confidence interval contains the value of 0 we don't have enough evidence to conclude that the difference between the two states for the salary of teachers are significantly different.

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