Intro to Psych; Module 3 (unit #1)

Statistical significance

a statistical statement of how likely it is that an obtained result occurred by chance.

Normal curve (normal distribution)

a symmetrical, bell-shaped curve that describes the distribution of many types of data; most scores fall near the mean (about 68 percent fall within one standard deviation of it) and fewer and fewer near the extremes.

Standard deviation

a computed measure of how much scores vary around the mean score.

Another name for a bell-shaped distribution, in which most scores fall near the middle and fewer scores fall at each extreme, is a ____ _____

normal curve

Mean

the arithmetic average of a distribution, obtained by adding the scores and then dividing by the number of scores.

How do we describe data using three measures of central tendency, and what is the relative usefulness of the two measures of variation?

Researchers use descriptive statistics to measure and describe characteristics of groups under study. A measure of central tendency is a single score that represents a whole set of scores. Three such measures that we use to describe data are the mode (most frequently occurring score) , the mean (arithmetic average), and the median (the middle score in a group of data). Measures of central tendency neatly summarize data; measures of variation tells us how diverse data are. Two measures of variation are the range (which describes the gap between the highest and lowest scores) an the standard deviation (how much scores vary around the mean, or average score) Scores often form a normal (bell-shaped) curve.

How do we know whether an observed difference can be generalized to other populations?

Researchers use inferential statistics (include ways of determining the reliability and significance of an observed difference between the results for different groups) to determine if results can be generalized to a larger population. Reliable differences are based on samples that are representative of the larger population being studied, that demonstrate low variability, on average, and that consist of many cases. We can say that an observed difference has statistical significance if the sample averages are reliable, and when the difference between them is large.

When sample averages are _________ and the difference between them is ___________ we can say the difference has statistical significance a. reliable; large b. reliable; small c. due to chance; large d. due to chance; small

a

Which of the three measures of central tendency is most easily distorted by a few very large or very small scores? a. the mode b. the mean c. the median d. they are equally vulnerable to distortion from atypical scores

b

The standard deviation is the most useful measure of variation in a set of data because it tells us a. the difference between the highest and lowest scores in the set b. the extent to which the sample being using deviates from the bigger population it represents c. how much individual scores differ from the mode d. how much individual scores differ from the mean

d

Range

the difference between the highest and lowest scores in a distribution.

Median

the middle score in a distribution; half the scores are above it and half are below it.

Mode

the most frequently occurring score(s) in a distribution.