Final answer:
The margin of error for a 95% confidence interval is approximately 2.170.
Step-by-step explanation:
To find the margin of error for a 95% confidence interval, we first need to calculate the standard error using the formula:
Standard Error = Standard Deviation / Square Root of Sample Size
Standard Error = 10.6 / Square Root of 91 = 1.108
The margin of error is then obtained by multiplying the standard error by the appropriate z-score for the desired confidence level:
Margin of Error = z * Standard Error
For a 95% confidence interval, the z-score is approximately 1.96:
Margin of Error = 1.96 * 1.108 = 2.170
Therefore, the margin of error for a 95% confidence interval with a sample mean of 78 and a standard deviation of 10.6 is approximately 2.170.