“Significance and Meaning: Analyzing and Interpreting the Data” Funding was provided through a Community Engagement Supplement to the Oregon Clinical and Translational Research Institute at Oregon Health & Science University (National Institute of Health/NCRR/NCATS grants UL1TR000128 and ACTRI0601).

“What we have here is a failure to communicate.”

The following presentation will not make you into a statistician. Disclaimer WARNING: The following presentation will not make you into a statistician.

What I hope it will do: Renew your familiarity with a few basic research concepts and terms Introduce a few concepts and terms that are commonly used when researchers analyze and try to understand data from studies Provide a foundation, on which you can build, that may make it easier to work in partnership with academic researchers

What We’ll Talk About Today Review Basic Terms and Concepts Association (Correlation) Exposure and Outcome (Independent & Dependant Variables) Study Designs Interpreting Data Comparing Groups Sampling from a Population Statistical Significance

What We’ll Talk About Today Review Basic Terms and Concepts Association (Correlation) Exposure and Outcome (Independent & Dependant Variables) Study Designs Interpreting Data Comparing Groups Sampling from a Population Statistical Significance

What We’ll Talk About Today Review Basic Terms and Concepts Association (Correlation) Exposure and Outcome (Independent & Dependant Variables) Study Designs Interpreting Data Comparing Groups Sampling from a Population Statistical Significance

Association (Correlation)

Association (Correlation) Overweight Ice Cream Consumption

Basic Terms Exposure (Independent variable): A state of contact with something or any relevant characteristic, habit, or practice that may increase or decrease the likelihood of an outcome Outcome (Dependent variable): A disease or other condition that results from an exposure

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Independent & Dependent Variables Cardiovascular Fitness (Outcome; Dependent Variable) Aerobic Exercise (Exposure; Independent Variable)

Cardiovascular Fitness Aerobic Exercise

Positive Correlation Cardiovascular Fitness Aerobic Exercise

Overweight Aerobic Exercise

Negative Correlation Overweight Aerobic Exercise

Study Design Types (Quantitative) Descriptive study Cross-sectional study Case-Control study Cohort study Randomized Trial

Four (very) basic stages of studies Pose a researchable question Design a study to get data to answer the question Gather data Analyze and interpret the data

Comparing one group with another…..

Which School has the Taller 7th Grade Boys?

Which School has the Taller 7th Grade Boys? Washington Jr. High Lincoln Jr. High

Which School has the Taller 7th Grade Boys? Washington Jr. High Lincoln Jr. High Sample: 1 boy Height = 62” (5 ft, 2 in)

Which School has the Taller 7th Grade Boys? Washington Jr. High Lincoln Jr. High Sample: 1 boy Height = 62” (5 ft, 2 in) Sample: 1 boy Height = 56” (4 ft, 8 in)

Which School has the Taller 7th Grade Boys? Washington Jr. High Lincoln Jr. High Sample: 1 boy Height = 62” (5 ft, 2 in) Sample: 1 boy Height = 56” (4 ft, 8 in) Conclusion: 7th Grade Boys at Washington Jr. High are Taller

Convinced?

What more do you want to know ?

Which School has the Taller 7th Grade Boys? Washington Jr. High Lincoln Jr. High Sample: 2 boys 1) 62” (5 ft, 2 in) 2) 54” (4 ft, 6 in) Sample: 2 boys 1) 56” (4 ft, 8 in) 2) 63 “ (5 ft, 3 in)

Which School has the Taller 7th Grade Boys? Washington Jr. High Lincoln Jr. High Sample: 2 boys 1) 62” (5 ft, 2 in) 2) 54” (4 ft, 6 in) Mean (average): [62 + 54] ÷ 2 = 116 ÷ 2 = 58” (4 ft, 10 in) Sample: 2 boys 1) 56” (4 ft, 8 in) 2) 63 “ (5 ft, 3 in) Mean (average): [56 + 63] ÷ 2 = 119 ÷ 2 = 59.5” (4 ft, 11½ in)

Which School has the Taller 7th Grade Boys? Washington Jr. High Lincoln Jr. High Sample: 35 boys Mean Height = 58.3” (4 ft, 10 in) Sample: 35 boys Mean Height = 58.1” (4 ft, 10 in)

Height: 7th Grade Boys Washington Junior High

Height: 7th Grade Boys Washington Junior High Sample

Height: 7th Grade Boys Lincoln Junior High

Height: 7th Grade Boys Lincoln Junior High Sample

Normal Distribution Curve

Which School has the Taller 7th Grade Boys? Washington Jr. High Lincoln Jr. High Mean (Average) = 58.4” Mean (Average) = 58.4” Sample = 62” Sample = 56”

Who’s Taller: 5th Grade Girls or 7th Grade Girls?

Who’s Taller: 5th Grade Girls or 7th Grade Girls? Sample: 1 girl Height = 58” (4 ft, 10 in) Sample: 1 girl Height = 56” (4 ft, 8 in)

Who’s Taller: 5th Grade Girls or 7th Grade Girls? Sample: 1 girl Height = 58” (4 ft, 10 in) Sample: 1 girl Height = 56” (4 ft, 8 in) Conclusion: 5th Grade Girls are Taller than 7th Grade Girls

Convinced?

What more do you want to know ?

Height: 5th Grade Girls

Height: 5th Grade Girls Sample

Height: 5th Grade Girls Sample 13 % of the group

Height: 7th Grade Girls

Height: 7th Grade Girls Sample

Height: 7th Grade Girls Sample 20 % of the group

Height: 5th and 7th Grade Girls 5th Grade Sample = 58”

Height: 5th and 7th Grade Girls 7th Grade Sample = 56” 5th Grade Sample = 58”

Who’s Taller: 5th Grade Girls or 7th Grade Girls? Sample: 30 girls Mean Height = 54” (4 ft, 6 in) Sample: 30 girls Mean Height = 58” (4 ft, 10 in) Conclusion: 7th Grade Girls are Taller than 5th Grade Girls

Height: 5th and 7th Grade Girls 7th Grade Mean = 58.8” 5th Grade Mean = 54.5” 7th Grade Sample = 56” 5th Grade Sample = 58”

When do we feel comfortable that our findings closely represent the real situation and are not just due to chance?

Statistical Significance What does it mean ?

Is the coin fair?

Probabilities of Consecutive Heads 1 Head 1 in 2 0.50 (50%) 2 Heads 1 in 4 0.25 (25%) 3 Heads 1 in 8 0.125 (12.5%) 4 Heads 1 in 16 0.063 (6.3%) 5 Heads 1 in 32 0.031 (3.1%) 6 Heads 1 in 64 0.016 (1.6%) 7 Heads 1 in 128 0.008 (0.8%)

Statistical Significance The probability that the result is due to chance is low.

Statistical Significance The probability that the result is due to chance is low. How low ?

Statistical Significance The probability that the result is due to chance is low. How low ? We choose….usually less than 5 %. (i.e., “p-value” < 0.05)

Statistical Significance What does it mean ?

Statistical Significance What does it mean ? That the findings are “true” ?

Statistical Significance What does it mean ? That the findings are “true” ?

Statistical Significance What does it mean ? That the findings are “true” ? That the study is of better quality ?

Statistical Significance What does it mean ? That the findings are “true” ? That the study is of better quality ?

Statistical Significance What does it mean ? That the findings are “true” ? That the study is of better quality ? That the findings are more important?

Statistical Significance What does it mean ? That the findings are “true” ? That the study is of better quality ? That the findings are more important?

What kind of Significance ? A program to increase exercise in kids: 4000 participants (2000 intervention; 2000 control) At baseline: Each group 60 min/week After intervention: - Intervention group: 62 min/week - Control group: 60 min/week - P-value = 0.03 (3 %)

Some Implications for Study Design Need to understand how large or small of a difference is important to detect Need to know how many study participants to include

Questions? Comments?