 |
Shopping Cart 
Checkout
|
 |
 |
|
|
|
|
Interpreting Data
After psychologists develop a theory, form a hypothesis, make observations,
and collect data, they end up with a lot of information, usually in the form of
numerical data. The term statistics refers to the analysis and
interpretation of this numerical data. Psychologists use statistics to organize,
summarize, and interpret the information they collect.
Descriptive Statistics
To organize and summarize their data, researchers need numbers to
describe what happened. These numbers are called descriptive
statistics. Researchers may use histograms or bar graphs to show the way data are distributed. Presenting
data this way makes it easy to compare results, see trends in data, and
evaluate results quickly.
| Course A | Course B | Course C | |||
| Student | Hours per week | Student | Hours per week | Student | Hours per week |
| Joe | 9 | Hannah | 5 | Meena | 6 |
| Peter | 7 | Ben | 6 | Sonia | 6 |
| Zoey | 8 | Iggy | 6 | Kim | 7 |
| Ana | 8 | Louis | 6 | Mike | 5 |
| Jose | 7 | Keesha | 7 | Jamie | 6 |
| Lee | 9 | Lisa | 6 | Ilana | 6 |
| Joshua | 8 | Mark | 5 | Lars | 5 |
| Ravi | 9 | Ahmed | 5 | Nick | 20 |
| Kristen | 8 | Jenny | 6 | Liz | 5 |
| Loren | 1 | Erin | 6 | Kevin | 6 |
To get a better sense of what these data mean, the researcher can plot
them on a bar graph. Histograms or bar graphs for the three courses might look
like this:
Measuring Central Tendency
Researchers summarize their data by calculating measures of
central tendency, such as the mean, the median, and the mode. The
most commonly used measure of central tendency is the mean,
which is the arithmetic average of the scores. The mean is calculated by
adding up all the scores and dividing the sum by the number of scores.
However, the mean is not a good summary method to use when the data
include a few extremely high or extremely low scores. A distribution with a
few very high scores is called a positively skewed distribution. A distribution with a few very low scores is called a negatively skewed distribution. The mean of a positively
skewed distribution will be deceptively high, and the mean of a negatively
skewed distribution will be deceptively low. When working with a skewed
distribution, the median is a better measure of central tendency. The median is the middle score when all the scores are arranged
in order from lowest to highest.
Another measure of central tendency is the mode. The mode is the most frequently occurring score in a distribution.
Measuring Variation
Measures of variation tell researchers how much the scores in a
distribution differ. Examples of measures of variation include the range and
the standard deviation. The range is the difference between the
highest and the lowest scores in the distribution. Researchers calculate the
range by subtracting the lowest score from the highest score. The standard deviation provides more information about the
amount of variation in scores. It tells a researcher the degree to which
scores vary around the mean of the data.
Inferential Statistics
After analyzing statistics, researchers make inferences about how reliable
and significant their data are.
If researchers want to generalize confidently from a sample, the sample
must fulfill two criteria:
- It must be large and varied enough to be representative.
- It must not have much variation in scores.
Researchers can use inferential statistics to figure out the
likelihood that an observed difference was just due to chance. If it’s unlikely
that the difference was due to chance, then the observed difference could be
considered statistically significant. Psychologists usually consider a result to
be statistically significant if such a result occurs just by chance
5 or fewer times out of every 100 times a study is done. They call this
statistical significance at the p ≤ .05 level (p less than or equal to point
oh-five).
However, statistical significance alone does not make a finding important.
Statistical significance simply means that a result is probably not due to
chance.
|
|
||||||||||||||||
|
||||||||||||||||
|
||||||||||||||||
©2006 SparkNotes LLC, All Rights Reserved.