lecture 1 variables + CI 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

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
where do biased measurements result from
systemic errors
26
what helps to eliminate error in regards to population size?
a larger population = less chance for error - cancel each other out - helps to tighten around mean/median
27
what does a wide box represent in a box and whisker plot
the wider the box in 25th and 75th percentile the more variability the error is - seen in smaller samples
28
histogram is also known as
frequency distribution plotted as a bar graph
29
how do you get the total number of values in a histogram?
you add the height of the bars
30
standard deviation define
the variation among values expressed in the same units as the data - spread of data around the mean/distribution
31
the larger the SD means...
the more spread out the distribution of data about the mean
32
data plotted on a frequency distribution tends to result in a....
SYMMETRICAL bell shaped curve
33
what is another name for bell shaped curve
Gaussian distribution
34
where do many of the values end up in the bell shape distribution?
near the center of the mean --few values end up farther away
35
vertical vs horizontal axis in the Gaussian Distribution curve
horizontal: various values that can be observed vertical: frequency
36
what is the relationship between the mean and median in a Gaussian Distribution curve?
they are both the SAME; distribution is symmetrical
37
what does the area under the Gaussian curve represent
the entire population
38
what is considered a standard normal curve
when the mean equals 0 and the SD equals 1.0 --> 68%
39
define variable "z"
the number of SD away from the mean
40
the "normal" distribution ____ define normal limits
does NOT
41
standard error of the mean (SEM)
the ratio of the SD dividied by the square root of the sample size
42
SEM does NOT directly quantify ____ or ____
scatter or variability
43
the ___ the sample size, the smaller the value of the SEM
larger
44
not a measure of the spread of the data,, but rather how well you know the population mean ....
SEM
45
SEM is always ___ than SD
smaller
46
what does a small SEM suggest?
that the sample mean is close to the population mean | -large sample size
47
the SEM can be used to construct _______ around a sample mean
confidence intervals
48
what values determine the Confidence Interval of a Mean
- sample mean - SD - sample size - degree of confidence
49
confidence interval of a mean is centered around ----?
sample mean
50
width of the confidence interval is ____ to the sample SD
proportional
51
what needs to be assumed in order to interpret CI of a mean?
- 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