7. Sampling Distributions & Confidence Intervals: Mean

Find $\alpha$ for a 90% confidence interval.

A market analyst is estimating the average monthly spending on online subscriptions among young adults. The point estimate y for the average monthly spending is $\mathrm{\backslash (}45.60$, with a margin of error $E$ of $\mathrm{\backslash )}3.20$ at a $90\%$ confidence level. Write and interpret a $90\%$ Confidence Interval for the average monthly spending.

Find the critical value, $z_{\frac{\alpha}{2}}$, for an 80% confidence interval.

A company is interested in estimating lunch costs in their cafeteria, so they survey employees asking for their monthly lunch expenses. The staff calculated a 95% confidence interval for the mean amount of money spent on lunch to be (\$580, \$720). What are the point estimate and margin of error for this sample data?