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Biostatistics > Chapter 1 > Flashcards

Chapter 1 Flashcards

1
Q

What are the two criteria for a random sample?

A
  1. Equal chance of being selected

2. Independent of each other

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2
Q

Explanatory variable

A

Independent variable
Predictor variable
Always on the x axis

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3
Q

Response variable

A

Dependent variable. What is being measured ? What do we want to predict ? Always on the y axis

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4
Q

Frequency distribution

A

Number of times each value of a variable occurs in a sample

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5
Q

What is the criteria for a good sample?

A 
Minimizing sampling error (precision ) 
Minimizing bias (accuracy)
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6
Q

Explanatory variable

A

Predictor variable

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7
Q

What 4 things do you look for when interpreting histograms?

A

Over all pattern?
What is the shape?
What is the spread?
Any striking deviations?

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8
Q

Graph to make with 2 categorical variables

A

Grouped bar graph

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9
Q

Graph to make with one categorical and one numerical variable

A

Bar graph

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10
Q

What does standard deviation measure ?

A

Measure of how different values are from the mean

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11
Q

How is standard deviation calculated ?

A

The square root of variance

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12
Q

What is coefficient of variation ?

A

Expresses the standard deviation as a percentage of the mean

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13
Q

What happens when the coefficient of variation increases ?

A

There is more variability

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14
Q

What is IQR ? How is it calculated ?

A

Inter quartile range = difference between the first and third quartile.

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15
Q

Which measurement methods are more sensitive to extremes?

A

Standard deviation and mean !

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16
Q

What three things describe the shape of a distribution ?

A

Symmetric or asymmetric ?
Center of data ?
Spread of data ?

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17
Q

What spread measurement is associated with median?

A

Inter quartile range

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18
Q

How do outliers affect mean? Median?

A

Mean increases

Median remains unchanged !

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19
Q

How does the mean relate to the median if the data is left skewed ?

A

Mean is larger than the median

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20
Q

How are mean and median related when the spread is symmetrical ?

A

Mean = median

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21
Q

What measure of location should be used if the distribution is symmetrical ?

A

Mean

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22
Q

What part of the box plot represents the IQR ?

A

The entire box

23
Q

What will a box plot look like if it is left skewed ?

A

Median line is closer to the top of the box

24
Q

What will a box plot look like if it is right skewed ?

A

The median line is closer to the bottom of the box

25
Q

Explanatory variable

A

Predictor variable

26
Q

What 4 things do you look for when interpreting histograms?

A

Over all pattern?
What is the shape?
What is the spread?
Any striking deviations?

27
Q

Graph to make with 2 categorical variables

A

Grouped bar graph

28
Q

Graph to make with one categorical and one numerical variable

A

Bar graph

29
Q

What does standard deviation measure ?

A

Measure of how different values are from the mean

30
Q

How is standard deviation calculated ?

A

The square root of variance

31
Q

What is coefficient of variation ?

A

Expresses the standard deviation as a percentage of the mean

32
Q

What happens when the coefficient of variation increases ?

A

There is more variability

33
Q

What is IQR ? How is it calculated ?

A

Inter quartile range = difference between the first and third quartile.

34
Q

Which measurement methods are more sensitive to extremes?

A

Standard deviation and mean !

35
Q

What three things describe the shape of a distribution ?

A

Symmetric or asymmetric ?
Center of data ?
Spread of data ?

36
Q

What spread measurement is associated with median?

A

Inter quartile range

37
Q

How do outliers affect mean? Median?

A

Mean increases

Median remains unchanged !

38
Q

How does the mean relate to the median if the data is left skewed ?

A

Mean is larger than the median

39
Q

How are mean and median related when the spread is symmetrical ?

A

Mean = median

40
Q

What measure of location should be used if the distribution is symmetrical ?

A

Mean

41
Q

What part of the box plot represents the IQR ?

A

The entire box

42
Q

What will a box plot look like if it is left skewed ?

A

Median line is closer to the top of the box

43
Q

What will a box plot look like if it is right skewed ?

A

The median line is closer to the bottom of the box

44
Q

What causes outliers?

A

Natural variation
Human error in recording
Human error in experimentation

45
Q

What is the observational unit ?

A

The subject that is being tested on

46
Q

How does the sample size affect a sampling distribution ?

A

If the sample size is increased then there will be less variation in the sample distribution. Precision is increased

47
Q

What does sampling distribution measure ?

A

Precision of an estimate

48
Q

What happens to the standard error of the mean as the sample size increases ?

A

As the sample size increases the standard error of the mean decreases

49
Q

Formula for SE?

A

S/ (square root of n)

50
Q

What does standard error describe?

A

The spread of the distribution of the sample means. Aka precision.

51
Q

What happens to standard deviation as sample size increases ?

A

The sd becomes more

Precise

52
Q

Name two measures of uncertainty

A

Confidence interval and standard error of the mean

53
Q

What is the unit of replication ?

A

Wherever the treatment is applied

54
Q

What does the confidence interval do ?

A

Quantifies the uncertainty about values

Biostatistics (2 decks)

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