Confidence Interval for the Estimated Mean of a Population

Given a sample of N values of X randomly drawn from a normally distributed population, this page will calculate the .95 and .99 confidence intervals (CI) for the estimated mean of the population, according to the formula
 estimatedpopulationmean = sample mean + (se x tcrit)
where:
 se = standard error of the mean; and tcrit = the two-tailed critical value of t for the .05 level of significance in the case of a .95 CI; and for the .01 level of significance in the case of a .99 CI

The page will also calculate various summary statistics for the sample.
 The logic and computational details of this procedure are described in Chapters 9 and 10 of Concepts and Applications.

• Importing Data via Copy & Paste:T
When importing data from a spreadsheet, the values of X must be in the form of a single column. Within the spreadsheet application, select and copy the column of data. Then return to this page, click the cursor into the data-entry field and perform the 'Paste' operation.T
• Direct Entry into Data Field:T
Click the cursor into the empty data-entry field, enter the first value of X, then press the carriage return key. Do the same for subsequent values of X, except that the final entry should not be followed by a carriage return.T
• Data Check:T
Make sure that the final line in the data-entry field entry is not followed by a carriage return. (An extra carriage return at the end of the list will be interpreted as an extra data entry whose value is zero. Importing data via the copy and paste procedure will almost always produce an extra carriage return at the end of a column.) After list of X values has been pasted into the data-entry field, click the cursor immediately to the right of the final entry in the list, then press the down-arrow key. If an extra line is present, the cursor will move downward. Extra lines can be removed by pressing the down arrow key until the cursor no longer moves, and then pressing the 'Backspace' key (on a Mac platform, 'delete') until the cursor stands immediately to the right of the final entry.T
• After verification of data entry, click the button labeled «Calculate». The results of the calculation will be displayed on a new page in the current browser frame. To return to the present page, click the «Back» button on your browser.

Data Entry:
 Please remember to perform the data-check procedure.

 Home Click this link only if you did not arrive here via the VassarStats main page.