1. Reasoning in Psychology Using Statistics
Spring 2017

2. Annoucements Exam 1 on Wednesday In lecture: closed book, scantron
In labs: open book, open notes
Annoucements

3. Sampling Population Sampling to make data collection manageable
Inferential statistics to generalize back
Sampling to make data collection manageable
Sample
Sampling

4. Inferential statistics
Where does “probability” fit in?
Population
Randomness in sampling leads to variability in sampling error
“Randomness” in short run is unpredictable but in long run is predictable
Allows predictions about likelihood of getting particular samples
Lots of samples n=5
Possible Samples
Examples: Odds in games of chance
Inferential statistics

5. Flipping a coin example: 1 flip
What are odds of getting heads?
One outcome classified as heads = 1 2
Total of two outcomes =
0.5
Flipping a coin example: 1 flip

6. Flipping a coin example: 2 flips
What are the odds of getting all heads?
One 2 heads outcome
Four total outcomes =
0.25
# of heads 2
What are the odds of getting only one heads?
Four total outcomes =
0.50
Two 1 heads outcome 1
Four total outcomes =
0.75
Three at least one heads outcome
What are the odds of getting at least one heads? 1
What are the odds of getting no heads?
Four total outcomes =
0.25
One no heads outcome
Flipping a coin example: 2 flips

7. Odds in Poker What are the odds of being dealt a “Royal Flush”?
Total number of possible outcomes
Total number of outcomes classified as A
Prob. of A = p(A) = 4
p(Royal Flush) = =
2,598,960
~1.5 hands out of every million hands
Odds in Poker

8. Odds in Poker What are the odds of being dealt a “Straight Flush”?
Total number of possible outcomes
Total number of outcomes classified as A
Prob. of A = p(A) = 40
p(straightflush) = =
2,598,960
~15 hands out of every million hands
Odds in Poker

9. Odds in Poker What are the odds of being dealt a …?
Total number of possible outcomes
Total number of outcomes classified as A
Prob. of A = p(A) =
Odds in Poker

10. Reviewing Producing Data
Scientific method
Research methods
Observation methods
Experimental methods
Quasi-experimental
Variables
Types
Operational definitions
Sampling
Samples and populations
Statistics and parameters
Techniques
Measurements
Continuous and discrete
Scales of measurement
Instrument
Errors in Measurement
Validity & Reliability
Confounds
Bias
Experimental control
Basic probability
SPSS data basics
Reviewing Producing Data

11. The researchers used a questionnaire to interview a random sample of 351 people ages 20 to 80 in the Vancouver, British Columbia, area, asking about their dog ownership and level of physical activity.
Dog owners walked almost twice as many minutes per week as people who did not own dogs, and the dog owners spent more time in all forms of mild and moderate physical activity.
Neither the sex of the owner nor the size of the dog made a difference: men and women who owned dogs participated in increased amounts of moderate exercise compared with those who had no dog. But no statistically significant difference between the two groups was evident in the amount of strenuous exercise performed.
The authors concede that the study, published in the February issue of The American Journal of Preventive Medicine, does not determine whether owning a dog itself makes people exercise more.
Shane Brown, the study's lead author and a graduate student at the Behavioral Medicine Laboratory of the University of Victoria, called this "the million-dollar question."
When the researchers subtracted the time spent walking the dog from total physical activity, dog owners actually walked less than their counterparts without dogs.
This, the researchers say, may suggest that the dog makes the difference. When dog owners choose to engage in moderate physical exercise, the reason may be that a four-legged member of the household is insisting on a walk. Now.
People who own dogs appear to get more exercise than those who do not …
Report (NY Times 2006): dog a more reliable exercise partner than a human.
In the news

12. In the research literature
Results
The analyses revealed that dog owners spent more time in mild and moderate physical activities and walked an average of 300 minutes per week compared to non–dog owners who walked an average of 168 minutes per week. A mediator analysis suggests that dog obligation acts as a mediator between dog ownership and physical activity. Moreover, the theory of planned behavior constructs of intention and perceived behavioral control explained 13% of the variance in walking behavior with an additional 11% variance in walking behavior being explained by dog obligation. Regarding intention to walk, the TPB explained 46% of the variance in intention to walk with dog obligation adding an additional 1% variance.
Conclusions
In this group of Canadians, those who owned a dog participated in more mild to moderate physical activity than those who did not. Acquiring a dog should be explored as an intervention to get people more physically active.
Background
Dog ownership may be an effective tailored intervention among adults for promoting physical activity. This study examined the relationship between walking, physical activity levels, and potential psychological mediators between people who owned dogs and those who did not own dogs in the Capital Region District of Greater Victoria, British Columbia, Canada. Data were collected in September 2004; analyses were conducted in January 2005.
Methods
A random sample of men (n=177) and women (n=174) aged 20 to 80 years participated. Questionnaires were mailed out in 2004 to collect information about demographics, dog ownership, leisure-time walking, physical activity levels, and theory of planned behavior (TPB) constructs.
Shane G. Brown, Bed. and Ryan E. Rhodes PhD
School of Physical Education, University of Victoria, Victoria, British Columbia, Canada
Available online 2 February American Journal of Preventive Medicine
In the research literature

13. In the news Research process Ask research question
Identify variables & formulate hypothesis
Define population
Select research methodology
Collect data from a sample
Analyze data
Draw conclusions based on data
Repeat
Regimens: Pounding the Pavement, Stopping at Fire Hydrants
People who own dogs appear to get more exercise than those who do not …
In the news

14. In the news Research process Context for our numbers
Ask research question
Identify variables & formulate hypothesis
Define population
Select research methodology
Collect data from a sample
Analyze data
Draw conclusions based on data
Repeat
Context for our numbers
Regimens: Pounding the Pavement, Stopping at Fire Hydrants
People who own dogs appear to get more exercise than those who do not …
In the news

15. In the news Research process Ask research question
Identify variables & formulate hypothesis
Define population
Select research methodology
Collect data from a sample
Analyze data
Draw conclusions based on data
Repeat
Regimens: Pounding the Pavement, Stopping at Fire Hydrants
People who own dogs appear to get more exercise than those who do not …
In the news

16. In the news Research process Variables Variables Ask research question
Identify variables & formulate hypothesis
Define your population
Select a research methodology
Collect your data from a sample
Analyze your data
Draw conclusions based on your data
Repeat
Variables
Operational level
Conceptual level
Regimens: Pounding the Pavement, Stopping at Fire Hydrants
Variables
Independent (explanatory) variables
Dependent (response) variable
Control variables
Random variables
Confound variables
The researchers …, asking about their dog ownership and level of physical activity.
Methods
…. Questionnaires were mailed out in 2004 to collect information about demographics, dog ownership, leisure-time walking, physical activity levels, and theory of planned behavior (TPB) constructs.
In the news

17. In the news Research process Scales of measurement
Ask research question
Identify variables & formulate hypothesis
Define your population
Select a research methodology
Collect your data from a sample
Analyze your data
Draw conclusions based on data
Repeat
Regimens: Pounding the Pavement, Stopping at Fire Hydrants
Instrument used?
Scales of measurement
Nominal
Ordinal
Interval
Ratio
The researchers …, asking about their dog ownership and level of physical activity.
- men & women, own dog or not
- mild, strenuous
Methods
…. Questionnaires were mailed out in 2004 to collect information about demographics, dog ownership, leisure-time walking, physical activity levels, and theory of planned behavior (TPB) constructs.
- time spent exercising
In the news

18. In the news Research process Ask the research question
Identify variables & formulate hypothesis
Define population
Select research methodology
Collect data from sample
Analyze data
Draw conclusions based on data
Repeat
Is the sample representative?
Is there bias in sample?
Regimens: Pounding the Pavement, Stopping at Fire Hydrants
The researchers used a questionnaire to interview a random sample of 351 people ages 20 to 80 in the Vancouver, British Columbia, area, (i.e., mailed out questionnaires)
Was it simple random sampling?
Stratified random sampling?
Etc.?
In the news

19. In the news Research process Causal Claims?? Which Research Method??
Ask research question
Identify variables & formulate hypothesis
Define population
Select research methodology
Collect data from sample
Analyze your data
Draw conclusions based on your data
Repeat
Regimens: Pounding the Pavement, Stopping at Fire Hydrants
Causal Claims??
The researchers used a questionnaire to interview a random sample of 351 people ages 20 to 80 in the Vancouver, British Columbia, area,
Which Research Method??
Observational study
Experimental methodology
Quasi-experimental methodology
The authors concede that the study… does not determine whether owning a dog itself makes people exercise more.
This may suggest that .. when dog owners choose to engage in moderate physical exercise, the reason may be that [the dog] is insisting on a walk.
Gather 2 key pieces of data for each person: dog ownership, exercise
In the news

20. In the news Research process Possible confounds?
Ask research question
Identify variables & formulate hypothesis
Define population
Select research methodology
Collect data from sample
Analyze your data
Draw conclusions based on your data
Repeat
Regimens: Pounding the Pavement, Stopping at Fire Hydrants
Possible confounds?
If follow-up experiment were designed, what would you do?
In the news

21. Reviewing Producing Data
Scientific method
Research methods
Observation methods
Experimental methods
Quasi-experimental
Variables
Types
Operational definitions
Sampling
Samples and populations
Statistics and parameters
Techniques
Measurements
Continuous and discrete
Scales of measurement
Instrument
Errors in Measurement
Validity & Reliability
Confounds
Bias
Experimental control
Basic probability
SPSS data basics
Reviewing Producing Data

22. The next 4 slides are Bonus material (not covered on Exam 1, only covered in lecture if it comes up and there is extra time)
Sampling and probability
Sampling with replacement
Sampling without replacement
Bonus material

23. Basics of probability: Derived from games with all outcomes known
Draw lettered tiles from bag
Bag contains:
A’s B’s and C’s.
Both upper and lower case letters A a b B c C
What’s the probability of getting an A (upper or lower case)?
Total number of outcomes classified as A
Prob. of A = p(A) =
= 2/6 = 0.33
Total number of possible outcomes
Sample space
Basics of probability: Derived from games with all outcomes known

24. What’s the probability of getting an A (upper or lower case) on the first pick and another on a second pick? A a b B c C
1/6
2/6 + a
First Pick:
Prob. of A = p(A) =
2/6 = 0.33 A
Second Pick: ? – it depends on how you sample
Sampling with replacement
Sampling without replacement
The probabilities of selecting the titles change from 1st to 2nd pick A a b B c C a b B c C A b B c C
2/6
1/5
1/5
Basics of probability

25. What’s the probability of getting an A (upper or lower case) on the first pick and another on a second pick? A a b B c C
Sampling with replacement
Sampling without replacement
(2/6)*(1/5) =
1st pick
2nd pick a A b B c C
30 total outcomes
2 outcomes of 2 A’s
2/30 =
1st picks
2nd picks
1st picks
2nd picks a a A b B c C A a A b B c C b a A b B c C B a A b B c C c a A b B c C C a A b B c C
36 total outcomes
4 outcomes of 2 A’s
4/36 = 0.11
(2/6)*(2/6) = 0.11
1st pick
2nd pick
Basics of probability

26. Most statistical procedures assume sampling with replacement
For large populations it turns out not to matter much
e.g., suppose your population is N=1,000,000. Starting probability of selecting a particular item 1 in 1,000,000.
Sampling with replacement, odds stay at 1 in 1,000,000
Sampling without replacement, odds change to 1 in 999,999 the change is so small that it may not matter
In experiments, you typically don’t want to use sampling with replacement because of the potential for lasting effects of your independent variable
Basics of probability