Exam 1 Flashcards
1
Q
define population
A
everyone or everything that could be examined
2
Q
example of population
A
an entire classroom of students
3
Q
define sample
A
the individuals or things that are actually looked at
4
Q
example of sample
A
a subset of students in the classroom that will be looked at
5
Q
define experimental unit (EU)
A
one individual or thing you take a measurement on
6
Q
example of an experimental unit
A
an individual in the classroom
7
Q
define a variable
A
what is measure on each experimental unit
8
Q
example of a variable
A
age
9
Q
what is data value
A
one observation
10
Q
example
A
a certain number of people at a certain age
11
Q
what is data
A
all observations
12
Q
example of data
A
list of ages of the entire group
13
Q
define statistic
A
sample summary information (sample mean)
14
Q
example of statistic
A
average age in sample size
15
Q
define parameter
A
true population summary information (population mean)
16
Q
example of parameter
A
average age of population
17
Q
define descriptive statistics
A
information/ description about the subset of individuals examined
18
Q
define inferential statistics
A
make inference to everyone using the description of the subset (taking descriptive statistics one step further)
19
Q
define qualitative ordinal
A
a variable ordered with qualitative data; i.e. good, better, best
20
Q
define quantitative discrete
A
a variable that uses whole numbers, i.e. # of people
21
Q
define quantitative continuous
A
a number that is cut off to a certain number of decimal places, such as length, height, time, etc.
22
Q
define qualitative nominal
A
a variable with a definitive name, or list; i.e. SSN or colors
23
Q
what makes a ‘good’ sample
A
must be:
- random: selected with some element of chance
- represent entire population: everyone could have been sampled
- must not have bias: bias has a direction in which some individuals have not been included in sample
- independence: every EU is independent of other EUs
24
Q
what is an experiment
A
a study in which a variable must be manipulated
25
what is a survey
a study in which data is simply collected from people
26
1. Which of the following is not considered an aspect of a “good” sample?
a. Random
b. Represents entire population
c. Large sample
d. Independence
C. Large sample
27
2. In an experiment to determine how the weight of a rat correlates to its likelihood of carrying a disease, what does the weight of an individual rat represent?
a. Variable
b. Experimental unit
c. Data value
d. Statistic
C. Data value
28
What is a judgment sample
a sample that can't meet the four aspects of a 'good' sample
29
Which variable is a discrete quantitative variable?
A. The weight of all the students from University of Maryland
B. The number of siblings of the students in BIOM 301 course
C. The eyes’ color of students aged from 18-22 in Maryland
D. The phone number of the student’s parents
B. The number of siblings of the students in BIOM301 course
30
```
WHICH ONE IS NOT A CHARACTER OF A GOOD SAMPLE
A. RANDOM
B. INDEPENDENT
C. SPECIFIC
D. REPRESENTS ENTIRE POPULATION
```
C. specific
31
What are the two main areas of statistics?
descriptive statistics and inferential statistics
32
Does a big sample necessarily mean a good sample?
No.
33
is a small sample a bad sample?
no
34
1) Which of the following is NOT a qualitative summary graph?
a) Circle graph
b) Stem and Leaf plot
c) Bar graph
B. Stem and Leaf Plot
35
2) Which of the following is NOT one of the 4 measures of central tendency?
a) mean
b) mode
c) sample variance
d) midrange
C. Sample Variance
36
List the three indicative properties of a normal curve
always symmetrical, unimodal, and bell-shaped
37
What value is r when there is no linear relationship?
zero
38
what are 4 correlation terms?
linked, associated, connected, and tied to
39
Describe 3 reasons why r can equal zero.
r can equal zero when:
- there is no relationship
- y changes but x does not and vice versa
- when the relationship is not linear
40
T/F correlation analysis is a method of obtaining the equation that represents the relationship between two variables
False; regression
41
t/f the linear correlation coefficient is used to determine the equation that represents the relationship between two variables
false, direction and tightness
42
t/f a correlation coefficient of positive or negative 1 means that the two variables are perfectly correlated
true
43
t/f whenever the slope of the regression line is zero, the correlation coefficient will also be zero
true
44
t/f when r is positive b(1) will be negative
false, positive
45
t/f the slope of the regression line represents the amount of change expected to take place in y when x increases by 1 unit
true
46
t/f correlation coefficients range between 0 and -1
false, -1 and +1
47
t/f the value being predicted is called the input variable
false, output variable
48
t/f the line of best fit is used to predict the average value of y that can be expected to occur at a given value of x
true
49
define bivariate data
data containing 2 observations for 1 experimental unit
50
correlation coefficient
statistical variable, r, representing a relationship's direction and tightness in respect to linear correlation data. Value range from -1 to +1
51
outlier
a datapoint that falls outside the range of bulk of the data set, can have a huge impact on statistical results
52
covariance
when variables vary together in some relationship. E.g. both X and Y variables values move from low to high.
• if X increases and Y decreases, this is also a pattern of co-variance
53
lurking variable
a third unmeasured variable that has a relationship to 2 variables and makes it appear that the measured variables are related to each other when actually they are related to the unmeasured variable.
54
regression
generates a relationship that explains how Y changes as a function of X
55
dependent or output variable
in terms of regression, the Y variable is the result of X (input variable)
56
independent or input variable
in terms of regression, the X variable that results in a certain outcome or Y variable
57
best fit line
a line in regression that minimizes the devation from data points to itself in the vertical direction
58
intercept b0
the statistic in the line of best fit that describes the intercept value when x = 0
59
slope b1
the statistic in the line of best fit that describes the direction of the relationship
60
R^2
a value of regression- how much variability in y varaible is explained by x variable. Value ranges from 0-1
61
prediction
a result of an observational or survey study analyzed using regression
62
causation
a result of a controlled or experimental study analyzed with regression
63
what graphs can be used to examine quantitative variables
box and whisker diagrams, stem and leaf diagrams and frequency histograms
64
what graphs can be used to examine qualitative variables
circle graphs and bar graphs
65
what must be present in a graph for it to be 'good'
- a title
- labeled axes w/ units if available
- a key if available
66
is there a space in a bar graph of qualitative data
yes
67
do frequency histograms have spaces between the bars?
no
68
in grouped frequencies, what does n equal?
the sample size
69
what is used to measure central tendency
- mean
- median
- mode
- midrange
70
what is the mean
the average
71
what is the median
the middle number
72
what is the mode
the most frequent observation
73
what is the midrange
the halfway point through the data (max + min)/2
74
if a graph is symmetric and unimodal, are the mean, median, and midrange the same? the Mode?
yes, yes
75
if a graph is symmetric and bimodal, are the mean, median, and midrange the same? the Mode?
yes, no
76
what is the mean sensitive to?
outliers
77
what is sample variance
avg squared difference in data set, in sq. units
78
what is sample standard deviation
the square root of the sample variance
79
in a density curve, the area under the curve represents what
100% of the data provided
80
what is the rounding rule
when you calculate a statistic, take the answer 1 decimal place further than the original data
81
what is a good way to hide the impact of a few large or small numbers? how can this be corrected?
use the mean to skew the results. report the median
82
how can graphs be confusing
- not being drawn to scale
- using pictures or figures instead of bars
- using 3-d graphs
- misrepresentation
83
does correlation mean causation
NO NO NO
84
what variable can two seemingly correlated variables actually be correlated to?
a lurking variable instead of each other
85
what are we asking for when we use a scatter plot
-is there a pattern?
| how can we interpret that pattern?
86
what two ways can we read scatter plots
correlation and regression
87
what can r tell us?
the direction and tightness of the relationship between x and y
88
in correlation, does flipping the axes influence r?
no
89
what can affect r?
outliers
90
what are some things to think about in regards to correlation
1. flipping axes does not influence r
2. changing one axis by a constant does not change r
3. outliers can influence r
4. lurking variables may be the cause of correlation
5. be sure you have the full range
6. do not draw conclusions outside of the range given
91
what is the goal of linear regression
to generate a relationship that explains how Y changes as a function of X
92
what does a best fit line do?
it minimizes deviations from data points to line in the VERTICAL DIRECTION
93
what is b0
the intercept
94
what is b1
the slope
95
what is R^2
how much variability in the Y variable is explained by x variable, ranges from 0-1. represents tightness, but does not explain direction
96
what explains direction in regression
the slope (b1)
97
what is an experiement
a process that gives 1 result
98
what is an outcome
all possible results
99
what is an event
1 outcome of interest
100
what is probability
the likelihood of an event
101
what are three ways to find probability
- theoretically
- empirically
- subjectively
102
what is the rule of large numbers
with repetition, empirical results will approach the expected theoretical probability
103
what 4 tools are given to think about probability
- tree diagrams (cant directly calc. prob.)
- venn diagrams (can)
- contingency tables (can)
- sample spaces (can)
104
survey or experiment
A researcher watches 100 people purchase soda at a vending machine and recorded whether they chose regular or diet soda.
survey
105
survey or experiment
Emergency room visitors complaining of stomach pain were randomly assigned to either a new drug treatment or a placebo.
experiment
106
survey or experiment
A researcher compares the medical records for 100 people that live near high-power electric lines to 100 people that don’t live near such lines. Survey or Experiment
survey
107
survey or experiment
. A researcher identified 20 students that got vigorous exercise at recess and then compared the grades of these students to a separate group of 20 who did not get vigorous exercise.
survey
108
what is one thing the frequency histograms show that relative frequency histograms do not?
sample size
109
The law of large numbers is used to calculate what?
emperical probability
110
Parameter of sample size
N
111
statistic of sample size
n
112
parameter of mean
mu symbol
113
statistic of mean
x (w/bar on top)
114
parameter of standard deviation
sigma
115
statistic of standard deviation
s
116
list the 4 aspects of a good sample
- random
- independent
- no bias
- covers entire population
117
T/F a normal curve is always unimodal
true
118
if P(A) = P(A ̅) then the P (A) = 0.5
true
119
t/f If two events are mutually exclusive, they are also independent
False
120
a scatter diagram is an appropriate display of bivariate data when both variables are quantitative
true
121
if the data points form a straight horizontal or vertical line, there is a strong correlation between the 2 variables.
False
122
What of the following would not be appropriate when considering 2 qualitative variables
2 histograms
2 bar graphs
2 circle graphs
2 histograms
123
T/F the value of the linear regression slope estimate will vary between -1 and +1
false
124
t/f the data is the list of observations recorded for each of the experimental units in your study
true
