Descriptive statistics

A planning guide for BIO 500 Week 7 Discussion 2, which asks why computing a variance of several numbers is like analysing their differences. There is a precise answer — variance is exactly a function of all the pairwise differences — and most posts never reach it.

SPSS will produce a mean for anything, including data where a mean is meaningless. The assignment is deciding which summary belongs to which variable, and then saying what the numbers show.

Three measures of centre on the same variable, and where they disagree is the finding. A submission that reports all three and comments on none has done the arithmetic and skipped the inquiry.

Using Table 2A's cross-tabulated systolic blood pressures for pill users and non-users aged 35-44, classify blood pressure and the group counts as continuous or discrete, build histograms for both groups and draw one conclusion, then explain why a normal approximation helps.

For ten given test scores, find the mean, median, mode, range, variance and standard deviation, then write a 500 to 750 word summary explaining which measure suits the data set, conducting a one-sample t-test against a population mean of 70, and saying when the information would be useful.

A two-part discussion: how graphics and statistics can be used to misrepresent data and where you have seen it done, and what characteristics of a population make mean, median or mode appropriate or inappropriate as a measure of centre.

Percentiles rank a student within their own form's group. That is exactly why they are limited here — and saying so is a better answer than computing something.