Day 3 2x2 Table 1

What are you curious about? From curiosity to a hypothesis From a hypothesis to questions From questions to answers From answers to counts From counts to prevalence From prevalence to statements Interpretation – Conclusions - Communication 2

3 Three main tools

1. Cross-sectional study design: a relatively quick way to test a hypothesis 4 An observational study A snapshot of what is going on Sometimes called a prevalence study One point in time

5 LANY

Cross-sectional studies are carried out to investigate possible associations between hypothesized exposures and outcomes. People in the study take a survey and give answers to questions about exposure and about outcome at the same time. From Epi Textbooks 6

What are you curious about? From curiosity to a hypothesis From a hypothesis to questions From questions to answers From answers to counts From counts to prevalence From prevalence to statements Interpretation – Conclusions - Communication 7 Cross-sectional study design

What are you curious about? From curiosity to a hypothesis From a hypothesis to questions From questions to answers From answers to counts From counts to prevalence From prevalence to statements Interpretation – Conclusions - Communication 8 Contingency Table

2. Contingency table: puts numbers in a table so we can get from answers to counts 9 Handy for calculations The simplest table is the 2x2 table Shows exposure and outcome

From Epi Textbooks A contingency table is used to display exposure and outcome data so associations can be measured. -Categories of one variable are presented in rows and categories of another variable are presented in columns -The table is used to show the number people who: have or do not have the exposure and have or do not have the outcome. -The simplest contingency table is the 2x2 table 10

Total On a sports team Not on a sports team Caffeine No Caffeine ExposureExposure Outcome ab cd 2x2 Table – Say it with numbers What people are in cell a? cell b? cell c? cell d? 11 Where are you?

Total ExposureExposure Outcome cd Is there a comparison group in this 2x2 table? If yes, where are they? 12 2x2 Table On a sports team Not on a sports team Caffeine No Caffeine

13 Comparison Group People who participate in a study and do not have the exposure of interest People whose results are compared to the group that was exposed

Total ExposureExposure Outcome Hypothesis: People who drink caffeine are more likely to be on a sports team. Which cell contains people who answer “yes” to both questions? 14 2x2 Table On a sports team Not on a sports team Caffeine No Caffeine a

Epi Team Challenge a b c d

ab dc An Apple a Day Keeps the Doctor Away Total 16

ab dc An Apple a Day Keeps the Doctor Away An Apple a Day Infrequent Doctor Visits No Apple a Day Frequent Doctor Visits Total 17

ab dc People who are not exposed dc An Apple a Day Keeps the Doctor Away Total 18 An Apple a Day Infrequent Doctor Visits No Apple a Day Frequent Doctor Visits

Total ab dc Study Links Physical Fitness to Academic Achievement 19

Total ab dc Study Links Physical Fitness to Academic Achievement Lower Grades Higher Grades 20 Physically Fit Not Physically Fit

Total ab dc People who are exposed ab Study Links Physical Fitness to Academic Achievement Physically Fit Lower Grades Higher Grades Not Physically Fit 21

ab dc Total Kids Who Watch R-Rated Movies More Likely to Drink or Smoke 22

ab dc R-Rated Movies Total Drink or Smoke Kids Who Watch R-Rated Movies More Likely to Drink or Smoke Do Not Drink or Smoke No R-Rated Movies 23

ab dc People who are exposed and have the outcome a Total Kids Who Watch R-Rated Movies More Likely to Drink or Smoke 24 R-Rated Movies Drink or Smoke Do Not Drink or Smoke No R-Rated Movies

ab dc Smoking Linked to Youth Eating Disorders Total 25

ab dc Smoking Linked to Youth Eating Disorders Smoke Eating Disorder Do Not Smoke No Eating Disorder Total 26

ab dc People who are exposed and do not have the outcome b Smoking Linked to Youth Eating Disorders Smoke Eating Disorder Do Not Smoke No Eating Disorder Total 27

ab dc Family Meals Are Good for Mental Health Total 28

ab dc Family Meals Are Good for Mental Health Family Meals Total Good Mental Health Poor Mental Health No Family Meals 29

ab dc People who are not exposed and do not have the outcome d Family Meals Are Good for Mental Health Total Good Mental Health Poor Mental Health 30 Family Meals No Family Meals

ab dc Study Links Iron Deficiency to Math Scores Total 31

ab dc Study Links Iron Deficiency to Math Scores Iron Deficiency Poor Math Scores No Iron Deficiency Good Math Scores Total 32

ab dc People who do not have the outcome and are not exposed d Study Links Iron Deficiency to Math Scores Poor Math Scores Good Math Scores Total 33 No Iron Deficiency Iron Deficiency

ab dc Proximity of Fast Food Restaurants to Schools and Adolescent Obesity Total 34

ab dc Proximity of Fast Food Restaurants to Schools and Adolescent Obesity Obese Not Obese Total 35 Fast Food Restaurant(s) Near School No Fast Food Restaurant(s) Near School

ab dc People who do not have the outcome d b Proximity of Fast Food Restaurants to Schools and Adolescent Obesity Obese Not Obese Total 36 Fast Food Restaurant(s) Near School No Fast Food Restaurant(s) Near School

ab dc Total Higher Risk of Obesity among Teens with More Video Game Playing 37

ab dc More Video Game Playing Obese Less Video Game Playing Not Obese Total 38 Higher Risk of Obesity among Teens with More Video Game Playing

ab dc Obese Not Obese Total People who are not exposed and have the outcome c 39 Higher Risk of Obesity among Teens with More Video Game Playing More Video Game Playing Less Video Game Playing

40 Yes / Yes No / No Yes / No No / Yes Cell a Cell b Cell c Cell d

41 Exposed Not Exposed Outcome No Outcome Total IMPORTANT NOTICE! Remember that any of the study types can use the idea of a 2x2 table to explore a possible association between and exposure and outcome

Breakout Assignment 2x2 table 42

From answers to counts Data into 2x2 Table CD C 43

44 - Fifty-four students were asked to participate in a cross- sectional study to explore the hypothesis: “Students who get more sleep are likely to be more physically active, compared to students who get less sleep.”

What is the exposure question? What is the outcome question?

46 Yes Exposure Yes Outcome Total No Outcome No Exposure ab dc Label the 2x2 table for the hypothesis

47 High Sleep High Physical Activity Total Low Physical Activity Low Sleep ab dc Label the 2x2 table for the hypothesis

What is the exposure question? What is the outcome question? Low Sleep High Sleep

49 High Sleep High Physical Activity Total Low Physical Activity Low Sleep ab dc Label the 2x2 table for the hypothesis

50 Deck Worksheet – Page 1 – Sort deck and fill out 2x2 table

51 For each survey, figure out which 2x2 table cell the respondent belongs (a, b, c, or d Write the correct letter of the cell in the upper left hand corner of each sheet Sort the 54 cards by cell letter Add up the numbers for each cell and fill in the 2x2 table accordingly -

52 Missing answers? -

53 Compare answers from the other teams in your school. -