Questions from Review Session

1. Will students be asked to produce the formulae for central tendency and dispersion?
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No, but you might well be asked to recognize them. My advice would be to understand what each measure does and how they differ from one another rather than rotely memorizing symbols. That is, if you understand conceptually what a standard deviation is and how it differs from variance or SE or SS, you should recognize its formula. Such recognition and understanding will be infinitely more useful to you in both the long- and short-term than simple memorization.

2. What is the unit of the standard error?
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The unit of the standard error is the original unit of measurement in the data set. Remember that the standard error provides an estimate of the precision of the mean. Said in another way, the SE defines the range around the sample mean in which the population mean is likely to lie. If the SE is large, your estimate of the mean is not very precise.

Imagine, for instance, that the obtained mean of all your grades in a given course was 91. If the standard error of that estimate were 1/2 point, you'd be feeling pretty confident about how much knowledge you really obtained. If, on the other hand, the SE were 50, this estimate of 91 could be very different from the true measure of your knowledge in the class. With a small standard error, we are more hopeful that our obtained mean more closely (a) represents the sample data and (b) approximates the population parameter.

3. What is the proper notation for population parameters and sample statistics?
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As noted in class, population parameters are typically indicated using Greek letters (which, by APA style guildelines, are never italicized) and sample statistics are indicated using italicized Roman letters. There are a few exceptions to this general rule, but we have not yet covered any of those exceptions.