lecture 1 variables + CI

Question 1

independent variable

Answer 1

Experimental or predictor variable
Can be manipulated in an experiment
Changed to have an effect on a dependent variable

Question 2

dependent variable

Answer 2

Outcome variable

Question 3

waht is the independent and dependent variable:

study being done to determine efficacy of new analgesic at different doses

Answer 3

Independent variable: dose of medication

Dependent variable: change in pain scale

Question 4

Nominal variable

Answer 4

categorical outcomes with MORE than two possible outcomes; not numeric

• categories in NAME only, w no particular order
  i. e. blood types A, B, AB, O
• -> there can be a mode but nO mean (avg b/t type A & B)

Question 5

Binomial (dichotomous) variable

Answer 5

categorical outcomes with TWO distinct possible outcomes

• subset of nominal
  i. e gender (yes/no)

Question 6

Ordinal variable

Answer 6

express rank and order matters (though not the exact value) (pain scale, level of education, restaurant ratings 1-5 stars)

Question 7

Continuous variable

Answer 7

represent data capable of possessing any value in a given range (BP, temperature, weight)

• NUMBER
  i. e. BP 110 to 120 is the same as 120 to 130–> 10 pt difference

Question 8

Interval variable

Answer 8

continuous spaced with equal intervals or distances; the zero point is not considered meaningful (example: IQ or temperature)
-diff b/w 5F and 4F is same as 60F to 59F

-0 degrees does not mean NO temperature, it can go lower **

Question 9

when you change the scale in the y axis (starts at 0 then change scale to 25) does it mean results are different?

Answer 9

no. it’s a matter of how data is represented, makes it look different but not

Question 10

Ratio variables

Answer 10

cant go below zero

Question 11

difference between interval and ratio

Answer 11

ratio can be calculated bc 0 point DOES matter

Question 12

mean

Answer 12

the average

- add all values and divide by total

Question 13

median

Answer 13

middle value

- put in order

Question 14

is the median influenced by the outliers

Answer 14

negative

Question 15

is the mean sensitive to outliers

Answer 15

yessss. –> mean wont be very representative

- it skews the result

Question 16

what does “n” mean in a study

Answer 16

number of observatiions

Question 17

what is the percentile of median

Answer 17

50%

Question 18

if the mean is very similar to the median…. this means….

Answer 18

not a lot of outliers

Question 19

trimmed mean

Answer 19

ignoring the highest and lowest (usually a percentage)

–removing influence of outliers*

Question 20

mode

Answer 20

value that occurs most commonly in data set

• not useful w continuous variables
• does not always assess the center of a distribution

Question 21

does the mode assess the center of a distribution

Answer 21

no

Question 22

error

Answer 22

variability in the data

Question 23

most of the scatter in biologic and clinical studies is due too…

Answer 23

biologic variation

i.e. aging, diet, mood

Question 24

bias

Answer 24

anything that skews the data one way or another

-influence study

Question 25

where do biased measurements result from

Answer 25

systemic errors

Question 26

what helps to eliminate error in regards to population size?

Answer 26

a larger population = less chance for error - cancel each other out - helps to tighten around mean/median

Question 27

what does a wide box represent in a box and whisker plot

Answer 27

the wider the box in 25th and 75th percentile the more variability the error is - seen in smaller samples

Question 28

histogram is also known as

Answer 28

frequency distribution plotted as a bar graph

Question 29

how do you get the total number of values in a histogram?

Answer 29

you add the height of the bars

Question 30

standard deviation define

Answer 30

the variation among values expressed in the same units as the data - spread of data around the mean/distribution

Question 31

the larger the SD means...

Answer 31

the more spread out the distribution of data about the mean

Question 32

data plotted on a frequency distribution tends to result in a....

Answer 32

SYMMETRICAL bell shaped curve

Question 33

what is another name for bell shaped curve

Answer 33

Gaussian distribution

Question 34

where do many of the values end up in the bell shape distribution?

Answer 34

near the center of the mean --few values end up farther away

Question 35

vertical vs horizontal axis in the Gaussian Distribution curve

Answer 35

horizontal: various values that can be observed vertical: frequency

Question 36

what is the relationship between the mean and median in a Gaussian Distribution curve?

Answer 36

they are both the SAME; distribution is symmetrical

Question 37

what does the area under the Gaussian curve represent

Answer 37

the entire population

Question 38

what is considered a standard normal curve

Answer 38

when the mean equals 0 and the SD equals 1.0 --> 68%

Question 39

define variable "z"

Answer 39

the number of SD away from the mean

Question 40

the "normal" distribution ____ define normal limits

Answer 40

does NOT

Question 41

standard error of the mean (SEM)

Answer 41

the ratio of the SD dividied by the square root of the sample size

Question 42

SEM does NOT directly quantify ____ or ____

Answer 42

scatter or variability

Question 43

the ___ the sample size, the smaller the value of the SEM

Answer 43

larger

Question 44

not a measure of the spread of the data,, but rather how well you know the population mean ....

Answer 44

SEM

Question 45

SEM is always ___ than SD

Answer 45

smaller

Question 46

what does a small SEM suggest?

Answer 46

that the sample mean is close to the population mean | -large sample size

Question 47

the SEM can be used to construct _______ around a sample mean

Answer 47

confidence intervals

Question 48

what values determine the Confidence Interval of a Mean

Answer 48

- sample mean - SD - sample size - degree of confidence

Question 49

confidence interval of a mean is centered around ----?

Answer 49

sample mean

Question 50

width of the confidence interval is ____ to the sample SD

Answer 50

proportional

Question 51

what needs to be assumed in order to interpret CI of a mean?

Answer 51

- random sample - independent observations (cant be measured twice) - accurate data - assessing an event you really care about - the population is distributed in a gaussian manner