Module 10

Question 0

how small does a p-value have to be before researchers feel results are not chance

Answer 0

p value of 0.05 or less is the cut-off point for researchers to have confidence in studies

Question 1

What is a P-Value

Answer 1

P-value assesses the probability that the results of the a study are due to chance or random error
for ex; a p-value of 0.05 tells us there is a 5% possibility that the results are due to random error or chance.

Question 2

Statistically signilficant

Answer 2

when the p value is less than 0.05

this means there are less than 5% probability 5/100 that the observed results were due to chance

Question 3

What three things influence the P-value

Answer 3

Magnitude of the effect (how much change in outcome actually occurred)
Sample size (how many people were in the study)
Variability (how different were the people in the study from one another)

Question 4

Magnitude of Effect

Answer 4

As the magnitude gets of effect gets larger, we become more confident the results are not due to chance alone (p-value gets smaller)

Question 5

Those with the greatest change… have the lowest p-value

Answer 5

true

Question 6

P-value and Sample Size

So as sample size increases….

Answer 6

If you flip a coin 10 x and it lands on heads 7 times are you confident?
The larger the sample size, the more confident you can be in the study’s results.

p- value decreases

Question 7

P-value and variability

Answer 7

as the variability gets smaller we become more confident that the results area not due to chance.. p value gets smaller

Question 8

Can you trust a study based on p-values?

Answer 8

No… must still consider bias, relevance of study, critically appraise the study methods

and if study is clinically important.

Question 9

what is power?

Answer 9

in studies about treatment, power is the ability of a study to detect a statistically significant result if one exists.

Question 10

1. Power depends on two things:

2. Where can I find info about power in a research article?

Answer 10

1. Sample size: were there enough subjects
   Magnitude of effect: was the size of the result large enough. large magnitude, more statistical power
2. Methods section

Question 11

How does p-value and power work together?

Answer 11

Power=the abilitly to FIND the significant result

p-value = the CONFIDENCE to know the result is not due to chance

Question 12

p-value is found where?

power is found where?

Answer 12

Results

methods

Question 13

confidence interval = range of effect

Answer 13

overall effect
range within true effect really lies
range of effect

Question 14

confidence interval

Answer 14

cyber bullying example
true effect 10% - 70% reduction
95% confidence level
low end of range might not make it worth it

Question 15

if confidence level crosses the 1 line?

Answer 15

-90% +10%

0% = the line of no difference
90% crosses the line, no better on either side of the line
The study does not suggest an effect.. We don’t have enough information or evidence. We would need a more narrow confidence interval(which would require greater statistical power)

Question 16

confidence intervals replace p-value

Answer 16

true

Question 17

clinical significance

Answer 17

pushes us to assess whether or not size of effectis big enough to justify the investment

95% confidence level

Question 18

creation of bike paths

Answer 18

led people to increase acti to 30 min /wk

confidence interval true effect 10 - 50 minutes 95/100

Question 19

bike path example

Answer 19

upper limit of CI 50 min increase
lower limit of CI 10 min increase . not impressive
assessing clinical significance…

Question 20

A CI of -90 to +10%

Answer 20

It is a 95% CI meaning we are 95 % confident that the difference falls w/in that range