1. Planning and Conducting a Study

2. What ways can you think of to collect data??
Data Collection
What ways can you think of to collect data??

3. Data Collection Surveys Other ways of collecting data
Telephone surveys
Mailed questionnaire
Personal interview
Other ways of collecting data
Surveying past records
Direct observation

4. Sampling Techniques
To obtain samples that are unbiased, statisticians use four basic methods of sampling: random, systematic, stratified, and cluster sampling.

5. Sampling Techniques Random Systematic
Samples are selected by using chance or random numbers
Examples:
Numbering each subject in the population. Place number cards into a bowl, mix, and choose as many as needed.
Numbering each subject of the population and then selecting every nth subject
Example:
Suppose there are 200 subjects in the population and a sample of 50 is needed. Since 200/50=40, you could take every 40th subject in the population to select for your sample.

6. Sampling Techniques Cluster Stratified
Dividing the population into groups (called strata) according to some characteristic that is important to the study, then sampling from each group.
Example:
President from a two-year college wants to learn how students feel about some issue. Furthermore, the president wishes to see if the opinions of the first-year students differ from the opinions of the second-year students. The president will select students from each group to use in the sample.
The population is divided into groups called clusters by some means such as geographic area or schools in a large school district, etc. Researcher randomly selects some of these clusters and uses all the members of the selected clusters as the subjects of the sample.
Example:
I want to survey apartment dwellers in a city. If there are 10 apartment buildings in the city, I can select at random 2 of the 10 and interview all of the residents of those 2 buildings.

7. Sampling Techniques Other techniques: Convenience sample
Researcher uses subjects that are convenient
Not the most representative technique – researcher has to check how representative the sample would be before conducting the survey/gathering the data.

8. Types of studies Observational Experimental
Researcher merely observes what is happening or what has happened in the past and tries to draw conclusions based on these observations
Researcher manipulates one of the variables and tries to determine how the manipulation influences other variables

9. Example 1: Article 1
Visit my teacher page and find the link for article 2 on Fighting racism: Teaching kids to identify individual black people can reduce racial bias.
State whether this is an observational or experimental study

10. Example 2: Article 2
Visit my teacher page and find the link for article 2 on High Blood Pressure in Midlife Tied to Later Dementia.
State whether this is an observational or experimental study

11. Example 3: Article 3
Visit my teacher page and find the link for article 2 on Brain stimulation can improve athletic performance.
State whether this is an observational or experimental study

12. Experimental studies - variables
Independent
Dependent
Variable that is manipulated by the researcher
Also called “explanatory variable”
Variable that is affected by the variable that the researcher manipulates
Also called “outcome variable”
Confounding variable
Variable that influences the dependent variable but was not separated from the independent variable

13. Experimental studies - groups
Treatment Group
Control Group
Group that received a specific treatment
Group that receives no treatment
Example: A researcher wants to see the effects of a certain weight loss drug. The researcher gives the pill to a group of 15 people and refrains from giving the pill to another 15 people. All 30 people are told to go on about their lives and not change anything about their diet or exercise regimen.
Treatment group: ???
Control group: ???

14. Treatment vs Control 1
You are testing to see if a new plant fertilizer increases sunflower size. You put 20 plants of the same height and strain into a location where all the plants get the same amount of water and sunlight. One half of the get the regular fertilizer. The other half of the plants get the fertilizer you are testing.

15. Treatment vs control 2
You are testing to see if a new drug works for asthma. You divide 100 volunteers into two groups of 50. One group of 50 gets the drug. The other 50 people get a sugar pill (a placebo).

16. Treatment vs control 3
You want to prove that covering meat prevents maggots from hatching. You put meat into two different jars: one with a lid and one left open.

17. Misuses of Statistics What are some reasons for misusing statistics??
How could someone take advantage of statistical results?

18. Some ways statistics can be misrepresented…
Suspect Samples
Ambiguous Averages
“Average”
Mean
Median
Mode
Midrange
These values can all be different, but a researcher can, without lying, select one of these values that lends most evidence to support their position.
Small samples
Volunteer samples
Convenience samples

19. Ways statistics may be misrepresented…
Changing the Subject
Detached Statistics
Different values are used to represent the same data
Example: 3% increase = $6,000,000 increase
Statistics in which no comparisons are made.
Example: These crackers have 1/3 less calories.

20. Ways Statistics may be misrepresented
Implied Connections
Misleading Graphs
Claiming a connection between variables that does not exist.
Use “may”, “suggest”, “work for some”
If graphs are drawn inappropriately, readers may draw false conclusions.

21. Ways statistics may be misrepresented…
Faulty Survey Questions
Phrasing of questions may trick the person answering
“always”, “never”, “only”
“Do you think the high school should build a new football stadium?” vs. “Do you favor increasing school taxes so that the school can build a new football stadium?”

22. In Summary…
Statistics, when used properly, can be beneficial in obtaining much information, but when used improperly, can lead to much misinformation.
Like your car – If you use your car to get to school or go visit friends, that’s good. But if you use it to run over your neighbor’s dog because it barks all night, that’s not so good.