##### Question

In: Statistics and Probability

# What is an 80% confidence interval? What does it mean for a confidence interval to be...

What is an 80% confidence interval?

What does it mean for a confidence interval to be ‘equal tailed?’

What are the steps for obtaining a confidence interval?

## Solutions

##### Expert Solution

# A Confidence Interval is a range of values we are fairly sure our true value mean lies in.

A 80% confidence interval has a 0.80 probability of containing the population mean. Or 80% of the population distribution is contained in the confidence interval.

# Equal-tailed Confidence interval means when for a given level of confidence the half of the area on the left side and  half of the area on the ride side are equal.

For a confidence interval with level C, the area in each tail of the curve is equal to (1-C)/2. For a 95% confidence interval, the area in each tail is equal to 0.05/2 = 0.025.

# Steps for confidence interval:

• Write down the phenomenon you'd like to test.
• Select a sample from your chosen population.
• Calculate your sample mean and sample standard deviation. ...
• Choose your desired confidence level. For example lets say 90%
• Calculate your critical value for the test. For example for 90% confidence interval,

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