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LECOM Biostats MS1 > Intro to Biostats--Lectures 1&2 > Flashcards

Intro to Biostats--Lectures 1&2 Flashcards

1
Q

What is the first step to take when developing research

A

Develop a hypothesis

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2
Q

What are the 4 steps of hypothesis testing

A
  1. Formulate a hypothesis
  2. Set criteria for decision
  3. Gather data and conduct statistical analysis
  4. Make decision (accept or reject)
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3
Q

What is a null hypothesis

A

States that two variables are not related

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4
Q

What are the two types of hypothesis used in hypothesis testing

A

Null hypothesis

Alternative hypothesis

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5
Q

What does a null hypothesis assume

A

no difference
all samples from some population
observed difference is due to chance
random sampling variation

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6
Q

What does an alternative hypothesis assume

A

at least one sample is from a different population

difference is not due to chance

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7
Q

How do you use a null hypothesis for testing

A

You try to disprove H0

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8
Q

If the probability of our result is less than alpha, then what is unlikely

A

that all samples came from the same population

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9
Q

What is alpha normally

A

0.05

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10
Q

When is a blood count considered normal

A

if value is found in 95% of the population and if independent of other tests

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11
Q

What are the two types of probability

A

mutually exclusive

independent

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12
Q

What is mutually exclusive probability

A

only one event can occur
either or
not both

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13
Q

What is independent probability

A

both things occur independently so you can have both

one even has no effect on the occurence of the other

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14
Q

How do you calculate mutually exclusive probabilities

A

addition rule

probability of X + probability of Y

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15
Q

How do you calculate independent probabilities

A

multiplication rule

probability of X x probability of y

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16
Q

What is sampling in statistics

A

selection of study subjects who will be measured on some parameter to provide information about population

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17
Q

What are the different sampling techniques

A 
simple random
stratified
systematic
multistage
convenience
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18
Q

What is the ultimate goal in sampling

A

want to avoid selection bias

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19
Q

What is selection bias

A

not giving people an equal chance to be selected

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20
Q

How is simple random sampling performed

A

each individual has an equal chance of having their name selected (draw names out of a hat)

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21
Q

How is systematic sampling done

A

select at regular intervals through ordered list

pick random number (k) and select kth person

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22
Q

What is stratified sampling

A

Separate people into strata and then select a sample from each group
keep the proportion of participants from each stratum equal

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23
Q

What is multistage sampling

A

combines more than 1 sampling

surveys sent out to randomly selected sample; from those answers select a more detailed survey

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24
Q

What are the types of variables based on how data is measured

A

Qualitative, quantitative

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25
Q

What are the variables based on study design

A

dependent and independent

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26
Q

What are the different types of qualitative (categorical) variables

A

Nominal
Dichotomous
Ordinal

27
Q

What are nominal variables

A

multiple categories with no difference in quality

28
Q

What are dicotomous variables

A

only two labels for variable

29
Q

What are ordinal variables

A

ranked variables

30
Q

What are the different types of quantitative variables

A

Interval

Ratio

31
Q

What is an interval variable

A

any quantitative vale

32
Q

What is a ratio variable

A

has meaning

33
Q

What are independent variables

A

input; manipulated

34
Q

What are dependent variables

A

outcome, response, predicted

35
Q

What is the standard P value that should be used in hypothesis testing

A

P<0.05

36
Q

What are the measures of central tendency

A

mean median mode

37
Q

What are the measures of dispersion

A

range, interquartile range, percentiles, SEM, SD, kurtosis, skewness, Confidence interval, Power, errors

38
Q

What is sample size and how does this affect statistical power

A

larger sample sizes tend to have more statistical power

39
Q

How do mean and median relate to distribution of a data set

A

if the same= normal distribution

if not the same= not normal distribution

40
Q

What is the function of descriptive statistics

A

describes data without generalizing population

41
Q

What is variance

A

spread of data

42
Q

What does 0 variance mean

A

identical values

43
Q

What is range

A

highest and lowest values

44
Q

What is interquartile range

A

difference between 25th and 75th percentiles

45
Q

What is standard deviation

A

square root of the variance

46
Q

How is standard error of the mean calculated

A

SD/ squareroot of sample size

47
Q

What will the SEM be in bigger groups compared to smaller groups

A

larger n= smaller SE

48
Q

How can we reduce variance

A

increase sample size
better define our sample populations
censor outliers

49
Q

What are the different types of normal unimodal distributions

A

Gaussian Distribution

Bell-shaped curve

50
Q

What are the different types of skewed unimodal distributions

A

left-skewed

right-skewed

51
Q

Describe a normal bell-shaped curve

A

1 standard deviation above and below the mean will include 2/3 of the data

95% will be within 2 standard deviations above and below the mean

52
Q

What is a skewed distribution

A

mean not equal to median

53
Q

What is a better measurement of the middle of the data in a skewed distribution

A

median

54
Q

What is a positive skew

A

right tail is longer; most values near y axis

mean> median> mode

55
Q

What is a negative skew

A

left tail is longer; most values on the right

mean< median< mode

56
Q

What is kurtosis

A

the “peakedness” of the distribution

57
Q

What is confidence interval

A

range of values in which a specified probability of the means of repeated samples would be expected to fall

58
Q

What are the different types of error

A 
Type 1 (alpha)
Type 2 (beta)
59
Q

What is a Type 1 alpha error

A

probability of rejection H0 when it is true

60
Q

What is a Type 2 beta error

A

probability of accepting H0 when it is false

61
Q

What is the probability of Type 1 error

A

false positive rate

62
Q

What is the probability of Type 2 error

A

false negative rate

63
Q

What is Power

A

probability of NOT committing Type II error

64
Q

How is Power calculated

A

1-beta

LECOM Biostats MS1 (3 decks)

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