Exam 2

Question 1

When values are taken from acutal data and the relative frequencies of occurence are calculated this is reffered to as?

Answer 1

Empirical Distribution

Question 2

How is statistical distribution defined?

Answer 2

• Defined by some theoretical probability distribution

Question 3

Normal distribution is also called?

• A normal distibution is any such distribution with a known? 2 things
• What two distribution can be known?

Question 4

What is a z-distribution

Answer 4

• A special type of normal distribution where the data have been transformed to follow the normal distibution with a mean of 0 and a standard deviation of 1.
• z=Xi-_X/_SD

Question 5

Xi+?

X line above?

Answer 5

Xi= observed value

Xline= mean value

Question 6

T-distribution

When is it used and why?

When does t approach Z?

Answer 6

• Usefule when the sample size is relatively small.
• T approaches Z when sample size increases

Question 7

T and Z are useful for continuous variables but not for?

Answer 7

Dont allow for categorical measurements

Question 8

Binomial distribution describes?

Answer 8

Described a random variable with two possible outcomes.

Which represents the simplest of a categorical outcome (success vs. failure)

Event happening p and event not happening q

Question 9

Calcualtion for risk of outcome?

Answer 9

Among Exposed= A/(A+B)

Unexposed= C/(C+D)

Question 10

Risk Ratio (Relative Risk)

Only done for what type of study?

What is the equation?

If =1?

If >1?

<1?

Answer 10

RR= Risk of Exposed/ Risk Unexposed

Fixed Cohort Study

If = 1 no difference between groups

>1 Then exposure increases risk of outcome occurence

<1 then exposure decreases risk of occurence

Question 11

Rate Ratio Calculation for what type of study?

equation

Answer 11

Incidence rate among exposed (A/person-time in exposed group)

/

The incidence rate among unexposed (C/person-time in unexposed group)

Question 12

ARR ( Risk difference or attributable risk)

Equation

Answer 12

Risk of exposed - risk of unexposed

RD= A/(A+B) - C/(C+D)

Question 13

Attributable fraction in the exposed (ARP)

Answer 13

ARP= [A/(A+B)-C/(C+D)]/(A/A+B) x 100

Question 14

Prevented Fraction In Exposed

?

Answer 14

PFE= 1-Risk Ratio

Question 15

Odds of being eposed In Case-Controlled Studies

Answer 15

Odds of being exposed A/C for cases

For controls B/D

Question 16

Odds ratio?

Answer 16

AxD/BxC

>1 exposure and outcome positively assoicated

<1 indicates exposure and outcome is negatively associated

Question 17

When is relative risk preferred over OR?

Answer 17

Preferred in prospective cohort studies and RCTs only.

Question 18

Information Bias

Occurs when errors in measurement

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