Title: Description and Correlation
1Description and Correlation
2 Reminder
- The last day to participate in experiments is
THIS FRIDAY (MARCH 9TH)!! - If you are writing a paper, it is due THIS FRIDAY
by 5pm - Give to Chris McFerron in Room 1813
3Outline
- What are statistics?
- Analyzing your results
- Frequency Distributions
- Measures of Central Tendency and Variability
- Correlations
4What are Statistics?
- A set of mathematical procedures for summarizing
and interpreting observations (data) - Goals
5Two Kinds of Statistics
- Descriptive Statistics
- Inferential Statistics
6Analyzing your Results
- 3 Basic Ways to Describe Results
- Compare group percentages
- Correlate scores of individuals on 2 variables
- Compare group means
7Compare Group Percentages
- How often do you wash your hands after using the
bathroom? - Always Sometimes Never
- Gender who said Always
- Female 82
- Male 79
8Compare Group Percentages, cont.
- I get cravings for chocolate
- Never Sometimes Fairly Often All
the Time - Gender who said Fairly Often or All the
Time - Female 60
- Male 15
9Correlate Scores
- Is stress correlated with chocolate cravings?
- When you are stressed, how likely are you to eat
more than usual? - 1 (Very unlikely) 7 (Very likely)
- I get cravings for chocolate
- Never Sometimes Fairly Often All
the Time -
10Correlate Scores, cont.
- Does waiting to have sex correlate with the
number of sexual partners one has? - I think it is acceptable to have more than one
sexual relationship at a time. - Strongly Disagree Disagree Undecided Agree
Strongly Agree - Approximately how long do you wait before having
sex with a person you are romantically involved
with? - ____until marriage
- ____5 years
- ____3 years
- ____1 year
- ____1 week
- ____1 day
-
11Compare Group Means
- On average, how many minutes per day do you spend
taking a shower? ____________
12Compare Group Means, cont.
- How many pairs of underwear do you own? _________
13Frequency Distributions
- Different Types of Frequency Distributions
- Table
- Pie Charts
- Bar Graphs
- Frequency Polygon
14Frequency Distributions Table
- When looking for a mate, I consider the following
qualities most important -
-
15Frequency Distributions Pie Chart
- When looking for a mate, I consider the following
qualities most important.
16Frequency Distributions Bar Graph
- When looking for a mate, I consider the following
qualities most important.
17Frequency Distributions Polygon
- When looking for a mate, I consider the following
qualities most important.
18Measures of Central Tendency and Variability
- Central Tendency
- Mean, median, mode
- Variability
- Range and standard deviation
19Measures of Central Tendency
- Mean
- Computed by summing scores and dividing the sum
by the number of individuals - Median
- The score or point in the distribution above
which half of the scores lie - Rank order the scores and select the middle score
- Mode
- The score that occurs most frequently
20Measures of Central Tendency Example
- Consider the following set of reading scores for
15 second graders - 31 33 35 38 40 41 41 41 44 46 47 48
49 49 51 - Mean 42
- Median ?
- Mode ?
21Measures of Central Tendency When to Use
- Now consider the following set of reading scores
for 15 second graders - 31 33 35 38 40 41 41 41 44 46 47 48
49 98 99 - Mean 48
- Median 41
- Mode 41
22Measures of Central Tendency When to Use, cont.
- It depends on the type of data you are
describing - Mean
- Median
- Mode
23Measures of Variability
24Measures of Variability Example
- Here are the heights for two groups of men
25Correlations
- A statistical value that assesses the
relationship between 2 variables - More specifically
- The direction of the relationship (/-)
- The form of the relationship (straight,
curvilinear) - The degree or strength of the relationship (-1 to
1) - Small relationship .10 - .20
- Medium relationship .30
- Large relationship gt.40
26Graphing Correlations
C
A
D
B
27Another Correlation from the Class Survey
- Do you think there is a relationship between the
following items? - I enjoy watching movies like The Notebook.
- I am concerned with how much I weigh.
28Tuesday
- Statistical Inference
- Cozby, Chapter 13