# Chapter 04

What do we mean by central tendency?

Define the mean. How do you find the mean of a sample? Can you write that formula symbolically?

When do we use the mean? With what kind of samples do we not use the mean?

What symbols represent the population mean and the sample mean?

Define the median. How do you find the median of a sample? With what kind of data do we use the median? What are the advantages of the median compared to (a) the mode and (b) the mean?

Define the mode. How do you find the mode of a sample? With what kind of data do we use the mode? What are the disadvantages of the mode?

What do these two symbols mean: ΣX2           and (ΣX)2

Can you use each symbol to perform calculations?

What is an outlier? What does it do to the mean?

Describe positive and negative skew. Be able to give/recognize an example of positive and negative skew in a sample.

What is variability? What does it tell us about a sample?

What is the range? How do you compute it?

What is variance?

What is the symbol for the sample variance? What is the symbol for population variance?

Be able to recognize and use the formula for variance.

What is standard deviation? How do you compute it?

What is the symbol for the sample standard deviation? What is the symbol for population standard deviation?

What is the relationship between the mean and standard deviation for a normal curve?

If you have the standard deviation and mean of a sample, can you compute the raw score that would be 1 or 2 standard deviations above and/or below the mean?

Be able to perform and interpret any SPSS procedures that we do for this chapter.