The diagram below gives practice at calculating a confidence interval for a linear model's slope.

The scatterplot on the left shows a bivariate data set and its least squares line. On the top right, the least squares slope is shown, together with the estimate of its standard deviation.

Use the green templates to evaluate the 95% confidence interval for β1:

  1. Evaluate the appropriate t-value (type the degrees of freedom and hit the return key)
  2. Type the two values that must be multiplied to give the '±' value and hit return.
  3. Type the resulting '±' value in the confidence interval at the bottom and click Check.

Repeat with different data sets until you feel confident with the method.