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Stats > midterm chapters 1-3 > Flashcards

midterm chapters 1-3 Flashcards

1
Q

CH 1-3 STATS

2 Types of Evidence

A

Observational

Evidential

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2
Q

CH 1-3 STATS

Anecdotal evidence

A

Evidence based on short stories or examples of interesting events

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3
Q

CH 1-3 STATS

Confounding variable

A

A variable that correlates with both the independent and dependent variables making it look like the two variables are directly related

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4
Q

CH 1-3 STATS

Placebo

A

An inert substance; a substance that looks like something else but is not composed of the same materials or ingredients
(ex. medicine vs. a sugar pill)

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5
Q

CH 1-3 STATS

Placebo effect

A

The tendency of people to respond favorably to any treatment, even if it is only inert

(Nocebo effect: the tendency of people to respond negatively to any treatment, even if it is only inert)

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6
Q

CH 1-3 STATS

Blinding

A

A technique used to keep the treatment assignment secret from the experimental subject

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7
Q

CH 1-3 STATS

Double-blinding

A

A technique used to keep the treatment assignments from both the experimental subjects and the persons making evaluations of the response

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8
Q

CH 1-3 STATS

Panel bias

A

Bias attributable to the study having influenced the behavior of the subjects

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9
Q

CH 1-3 STATS

Historical Controls

A

Controls are previous patients with the same illness who were treated with a different therapy than the one in question

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10
Q

CH 1-3 STATS

Problem with historical controls

A

Often there is a tendency for later patients to show a better response (even to the same therapy) than the previous patients with the same diagnosis

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11
Q

CH 1-3 STATS

Population

A

All subjects/animals/specimens/plants, and so on, of interest

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12
Q

CH 1-3 STATS

Sample (size n)

A

Subset of the population

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13
Q

CH 1-3 STATS

Effect of a biased sample

A

A biased sample systematically overestimates or systematically underestimates a characteristic of the population

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14
Q

CH 1-3 STATS

Qualifications of a simple random sample

A

a) Every member of the population has the same chance of being included in the sample
b) The members of the sample are chosen independently of each other

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15
Q

CH 1-3 STATS

Qualifications of a nonsimple random cluster sample

A

a) IDs are assigned to entire groups of individuals

b) Entire groups of individuals are selected for the sample

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16
Q

CH 1-3 STATS

Qualifications of a nonsimple stratified random sample

A

a) Population is divided into strata

b) Many random samples are taken-one within each stratum-and combined to comprise the sample

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17
Q

CH 1-3 STATS

Chance error due to sampling (sampling error)

A

A discrepancy between the sample and the population

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18
Q

CH 1-3 STATS

Sampling bias

A

Systematic tendency for some individuals of the population to be selected more readily than others

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19
Q

CH 1-3 STATS

Nonsampling error

A

Error that is not caused by the sampling method; An error that would have arisen even if the researcher had a census of the entire population

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20
Q

CH 1-3 STATS

Nonresponse bias

A

A bias caused by persons not responding to some of the questions in a survey or not returning a written survey

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21
Q

CH 1-3 STATS

Missing data

A

Observations that were planned but could not be made

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22
Q

CH 1-3 STATS

Variable

A

A characteristic of a person or a thing that can be assigned a number or a category

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23
Q

CH 1-3 STATS

Categorical variable

A

A variable that records which of several categories a person or thing is in

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24
Q

CH 1-3 STATS

Ordinal variable

A

A categorical variable in which the categories can be arrayed in a meaningful rank order

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25
Q

CH 1-3 STATS

Numeric variable

A

A variable that records the amount of something

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26
Q

CH 1-3 STATS

Continuous variable

A

A numeric variable that is measured on a continuous scale (includes decimals, fractions, etc.)

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27
Q

CH 1-3 STATS

Discrete variable

A

A numeric variable for which we can list the possible variables (integers)

28
Q

CH 1-3 STATS

Observational unit

A

The persons or things on which we are measuring variables

29
Q

CH 1-3 STATS

Frequency distribution

A

A display of the frequency (number of occurrences) of each value in the data set

30
Q

CH 1-3 STATS

Bar chart

A

A simple graphic showing the categories that a categorical variable takes on and the number of observations in each category for the data in the sample

31
Q

CH 1-3 STATS

Dotplot

A

A simple graph that can be used to show the distribution of a numeric variable when the sample size is small

32
Q

CH 1-3 STATS

Histogram

A

Like a bar chart, except that a histogram displays a numeric variable, which means that there is a natural order and scale for the variable

33
Q

CH 1-3 STATS

Relative frequency

A

= Frequency / n

34
Q

CH 1-3 STATS

Mode

A

The central peak in a frequency distribution; the value with the most occurences

35
Q

CH 1-3 STATS

Skewed to the right

A

The right tail is more stretched out than the left

36
Q

CH 1-3 STATS

Skewed to the left

A

The left tail is more stretched out than the right

37
Q

CH 1-3 STATS

Unimodal

A

The graph has only one mode

38
Q

CH 1-3 STATS

Bimodal

A

The graph has two modes: can indicate the existence of two distinct subgroups of observational units

39
Q

CH 1-3 STATS

Median ( ỹ)

A

The value that most nearly lies in the middle of the sample–the value that splits the ordered data into two equal halves

1/2 (n+1) denotes the rank position of the median within an ordered data set

40
Q

CH 1-3 STATS

Mean ( ȳ)

A

Sum of the observations divided by the number of observations (average)

41
Q

CH 1-3 STATS

Robust statistic

A

A statistic that is relatively unaffected by changes in a small portion of the data (even if the changes are dramatic ones)

42
Q

CH 1-3 STATS

Boxplot

A

A visual representation of the five number summary

43
Q

CH 1-3 STATS

Five number summary

A

Minimum, Quartile 1, Median, Quartile 3, Maximum

44
Q

CH 1-3 STATS

First quartile (Q1)

A

Median of the data values in the lower half of the data set (between the minimum and median)

45
Q

CH 1-3 STATS

Third quartile (Q3)

A

Median of the data values in the upper half of the data set (between the median and maximum)

46
Q

CH 1-3 STATS

Interquartile Range (IQR)

A

The difference between the first and third quartiles

47
Q

CH 1-3 STATS

Outlier

A

A data point that differs so much from the rest of the data that it doesn’t seem to belong with the other data

upper fence = Q1 - 1.5 * IQR

lower fence = Q3 - 1.5 * IQR

48
Q

CH 1-3 STATS

Modified boxplot

A

A boxplot in which the outliers are graphed as separate points

49
Q

CH 1-3 STATS

Univariate summary

A

A graphical or numeric summary of a single variable

50
Q

CH 1-3 STATS

Bivariate summary

A

A graphical summary used to examine the relationship between pairs of variables

51
Q

CH 1-3 STATS

Categorical-categorical relationship graphs

A

Bivariate frequency table
Stacked bar chart

Stacked relative frequency bar chart

52
Q

CH 1-3 STATS

Numeric-categorical relationship graphs

A

side-by-side boxplots

side-by-side dotplots

53
Q

CH 1-3 STATS

Numeric-numeric relationship graphs

A

Scatterplot

54
Q

CH 1-3 STATS

Scatterplot

A

A graph that examines the relationships between two numeric variables, X and Y

55
Q

CH 1-3 STATS

Lowless smooth line

A

A line on a scatterplot that is helpful in visualizing curved or nonlinear relationships in data

56
Q

CH 1-3 STATS

Regression line

A

A line in scatterplots that is helpful in visualizing linear trends in data

57
Q

CH 1-3 STATS

Range

A

The difference between the largest (maximum) and smallest (minimum) observations in a sample

58
Q

CH 1-3 STATS

Standard deviation (s)

A
  1. find the deviations for all data points
  2. square all
  3. add all together
  4. divide the sum by n-1
  5. take the square root
59
Q

CH 1-3 STATS

Coefficient of variation

A

The standard deviation expressed as a percentage of the mean

(standard deviation / mean) * 100%

60
Q

CH 1-3 STATS

The empirical rule

A

68% within 1 standard deviation of the mean
95% within 2 standard deviations of the mean

> 99% within 3 standard deviations of the mean

61
Q

CH 1-3 STATS

Population mean (μ)

A

= population average value of Y

Y=quantitative variable

62
Q

CH 1-3 STATS

Population Standard Deviation (σ)

A

=square root (population average value of (Y - μ)^2)

Y=quantitative variable

63
Q

CH 1-3 STATS

Sample Variance (s^2)

A

Square of the standard deviation (s)

64
Q

CH 1-3 STATS

Effect of addition on the transformation of variables

A
  • Linear transformation
  • Add constant, c, to the variables
  • Has no effect on standard deviation
65
Q

CH 1-3 STATS

Effect of multiplication on the transformation of variables

A
  • Linear transformation
  • Multiply values by constant, c
  • Multiply standard deviation by absolute value of c

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