## Confidence Level

Because you used 0.05 as the cut-off value in determining the plausible values, we call the interval of plausible values you just found a 95% confidence interval. Here, 95% is the *confidence level*, and provides a measure of the *reliability* of our method. Our interpretation is that we are 95% confident that the probability a kissing couple turns right is inside the interval.

(j) Calculate the *midpoint* of your interval by averaging the two endpoints. Does this value seem familiar? Why does that make sense?

(k) Calculate the *half-width* of your interval by subtracting the endpoints and dividing by two.

This value is often referred to as the margin-of-error and many confidence intervals have the form estimate , where the margin-of-error measures the accuracy of our statistic, how close we think we are to the actual parameter value.+ margin-of-error |

(l) Suppose we used 0.01 as the cut-off value instead. Use the table you created in (i) to determine the interval of plausible values. What is the corresponding confidence level? Write a sentence interpreting this interval in context.

(m) How did the margin-of-error change when we changed the confidence level? Explain why this change makes sense intuitively.