Statistical Methods for Psychology

18 Chapter 2 Describing and Exploring Data Table 2.2 Frequency distribution of reaction times Reaction Time, in Reaction Time, i ...

together into a histogram.^1 Our goal in doing so would be to obscure some of the random “noise” that is not likely to be meanin ...

would be classed as being in the interval. For example, had we recorded reaction times to the nearest thousandth of a second, ra ...

Notice in Figure 2.2 that the reaction time data are generally centered on 50–70 hun- dredths of a second, that the distribution ...

we will put that off until the next chapter. For now it is sufficient to say that we will often assume that our data are normall ...

that the score could have been 73 or 86, but it is not at all likely that the score would have been 20 or 100. In other words th ...

neurosciences and health sciences, techniques like kernel density plots are becoming more common. There are a number of technica ...

2, 3, and so on, are called thetrailing(or less significant) digits.They form the leaves— the horizontal elements—of our display ...

Notice that in Figure 2.8 I did not list the extreme values as I did in the others. I used the word High in place of the stem an ...

2.5 Describing Distributions The distributions of scores illustrated in Figures 2.1 and 2.2 were more or less regularly shaped d ...

28 Chapter 2 Describing and Exploring Data 4.0 Score (a) Normal 0.04 0.03 0.02 0.01 –4.0 –2.4 –0.8 0.8 2.4 25 Score (c) Negative ...

the data points are smoothly distributed between roughly 7 and 17 hundredths of a second, but a small but noticeable cluster of ...

trials. To obtain this knowledge, we must reduce the data to a set of measures that carry the information we need. The questions ...

they were absent from school (Y). The data and simple summation operations on them are illustrated in Table 2.4. Some of these o ...

2.7 Measures of Central Tendency We have seen how to display data in ways that allow us to begin to draw some conclusions about ...

A term that we will need shortly is the median location.The median location of N numbers is defined as follows: Median location ...

The Mode The mode is the most commonly occurring score. By definition, then, it is a score that ac- tually occurred, whereas the ...

The Mean Of the three principal measures of central tendency, the mean is by far the most common. It would not be too much of an ...

Wilcox has done a great deal of work on the problems of trimming, and I certainly re- spect his well-earned reputation. In addit ...

Section 2.8 Measures of Variability 37 Figure 2.12 Distribution of infant weight as a function of age We suspect that composites ...