To change the interval bar options
main topic      examples 

1    Select and double-click all interval bars. See Selecting groups and single items.

2    Click the Options tab.

3    Under Type of Interval, choose one of the following:

·    Standard error to display standard error bars, where the error bars extend one or more standard errors away from the mean.

-    In Multiple, enter a positive number to be used as the multiplier for standard errors (1 is the default).

·    Confidence interval to display confidence intervals. The confidence intervals assume a normal distribution for the data and use t-distribution critical values.

-    In Level, enter a number between 0 and 100 to specify the confidence level. The default is 95%. The interval bar endpoints correspond to the values of a confidence interval for the mean.

-    Check Bonferroni to calculate Bonferroni intervals.

4    From Side, choose the location of the bars. When you choose two-sided, bars are drawn above and below the mean. Upper one-sided gives bars above; lower one-sided draws bars below the mean.

For confidence intervals (default), the one-sided bars are shorter than the same side of the two-sided bars because Minitab uses a one-sided test. For standard error bars, the distance that error bars extend above or below the mean remains the same regardless of the selected side.

5    Check Pool error across groups to use the pooled degrees of freedom to calculate the critical value from the t-distribution for confidence interval bars, or a pooled standard error instead of calculating the error for each subgroup for standard error bars.

6    Click OK.