Difference Between Two Means

On the Stats tab, in the Assay Quality Control group: Select Difference Between Two Means to compare the true means of two populations using a sample from each.

To estimate the mean of a population from a sample, click Mean:

Input Populations

File

In the Difference Between Two Means form, select a file Type and then double-click (or click on the Select icon) to select the name of the Files containing the sample values. If required, define a Filter to selectively control which records will be processed.

Field

For each population, double-click (or click on the List icon) to select the name of the field containing the values for which statistics will be generated.

Standard deviation

Enter a known standard deviation of the samples. The estimate will be enhanced if you are able to enter a standard deviation for each population. The following cases can apply:

  • The standard deviations of the two populations are unknown
  • The standard deviations of the two populations are unknown, but they are known to be equal
  • Both standard deviations are known

Population 1 and Population 2 settings in the Difference Between Two Means form

Numeric Exceptions

(Optionally) Use the Numeric Exceptions group to control the way that non-numeric values are handled. Non-numeric values include characters, blanks, and values preceded by a less than sign (<).

Confidence Level

Enter a percentage that will determine the range of sample means that will include the true mean. For example, to be 90% confident, we estimate that the sample mean is somewhere in the middle 90% of the distribution of the sample means.

Increasing the confidence level has the effect of increasing the range within which the estimated mean can fall.

Same standard deviation

When the standard deviations of the two populations are unknown, but they are known to be equal, select this option to apply the same standard deviation to both populations.

Forms

Click the Forms button to select and open a saved form set, or if a form set has been loaded, save the current form set.

Calculate

Click Calculate to calculate the statistics. The results are shown on the right-hand of the form. Click Copy to Clipboard to copy the results. You can then paste them into a spreadsheet or text document.

Lo Diff and Hi Diff give the estimated range of values for the difference between the means.