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Epi Bio > lecture 1 variables + CI > Flashcards

lecture 1 variables + CI Flashcards

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Biology 101 flashcards
1
Q

independent variable

A

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

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2
Q

dependent variable

A

Outcome variable

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3
Q

waht is the independent and dependent variable:

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

A

Independent variable: dose of medication

Dependent variable: change in pain scale

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4
Q

Nominal variable

A

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)
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5
Q

Binomial (dichotomous) variable

A

categorical outcomes with TWO distinct possible outcomes

  • subset of nominal
    i. e gender (yes/no)
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6
Q

Ordinal variable

A

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

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7
Q

Continuous variable

A

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
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8
Q

Interval variable

A

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 **

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9
Q

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

A

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

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10
Q

Ratio variables

A

cant go below zero

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11
Q

difference between interval and ratio

A

ratio can be calculated bc 0 point DOES matter

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12
Q

mean

A

the average

- add all values and divide by total

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13
Q

median

A

middle value

- put in order

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14
Q

is the median influenced by the outliers

A

negative

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15
Q

is the mean sensitive to outliers

A

yessss. –> mean wont be very representative

- it skews the result

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16
Q

what does “n” mean in a study

A

number of observatiions

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17
Q

what is the percentile of median

A

50%

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18
Q

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

A

not a lot of outliers

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19
Q

trimmed mean

A

ignoring the highest and lowest (usually a percentage)

–removing influence of outliers*

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20
Q

mode

A

value that occurs most commonly in data set

  • not useful w continuous variables
  • does not always assess the center of a distribution
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21
Q

does the mode assess the center of a distribution

A

no

22
Q

error

A

variability in the data

23
Q

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

A

biologic variation

i.e. aging, diet, mood

24
Q

bias

A

anything that skews the data one way or another

-influence study

25
Q

where do biased measurements result from

A

systemic errors

26
Q

what helps to eliminate error in regards to population size?

A

a larger population = less chance for error

  • cancel each other out
  • helps to tighten around mean/median
27
Q

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

A

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

28
Q

histogram is also known as

A

frequency distribution plotted as a bar graph

29
Q

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

A

you add the height of the bars

30
Q

standard deviation define

A

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

31
Q

the larger the SD means…

A

the more spread out the distribution of data about the mean

32
Q

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

A

SYMMETRICAL bell shaped curve

33
Q

what is another name for bell shaped curve

A

Gaussian distribution

34
Q

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

A

near the center of the mean

–few values end up farther away

35
Q

vertical vs horizontal axis in the Gaussian Distribution curve

A

horizontal: various values that can be observed
vertical: frequency

36
Q

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

A

they are both the SAME; distribution is symmetrical

37
Q

what does the area under the Gaussian curve represent

A

the entire population

38
Q

what is considered a standard normal curve

A

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

39
Q

define variable “z”

A

the number of SD away from the mean

40
Q

the “normal” distribution ____ define normal limits

A

does NOT

41
Q

standard error of the mean (SEM)

A

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

42
Q

SEM does NOT directly quantify ____ or ____

A

scatter or variability

43
Q

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

A

larger

44
Q

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

A

SEM

45
Q

SEM is always ___ than SD

A

smaller

46
Q

what does a small SEM suggest?

A

that the sample mean is close to the population mean

-large sample size

47
Q

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

A

confidence intervals

48
Q

what values determine the Confidence Interval of a Mean

A
  • sample mean
  • SD
  • sample size
  • degree of confidence
49
Q

confidence interval of a mean is centered around —-?

A

sample mean

50
Q

width of the confidence interval is ____ to the sample SD

A

proportional

51
Q

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

A
  • 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

Epi Bio (4 decks)

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