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Summer 2014 > Stats Final Exam > Flashcards

Stats Final Exam Flashcards

1
Q

What type of data is collected through a count?

A

Discrete quantitative

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2
Q

What type of data is collected through measurement

A

Continuous quantitative

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3
Q

What type of data is categorical?

A

Qualitative

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4
Q

What are the 3 principles of experimental design?

A
  1. Control
  2. Randomization
  3. Replication
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5
Q

What is the difference between observation and experiment

A
  • o= observe + take measurements, data that already exists
  • e= impose treatments and controls// one variable is the cause of changes
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6
Q

This is an experimental condition that determine the levels of single/multifactors

A

experimental treatment

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7
Q

What is the sampling method used to eliminate bias?

A

Simple Random Samples (SRS)

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8
Q

What are 3 biased sampling schemes?

A

convenience sampling, voluntary response sampling, nonresponse sampling

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9
Q

A call-in radio show that solicit audience participation in surveys on controversial topics like abortion is an example of

A

voluntary response sample

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10
Q

This is a variable that is not the explanatory variable but is thought to affect the response variable

A

Confounding, lurking

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11
Q

When can confounding variables be a problem?

A
  • The results show a false correlation btwn dependent and independent variables,
  • Null hypothesis.
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12
Q

Why is control, randomization, + replication important?

A

differences in the results of an experiment are not attributed to chance but are caused by treatments.

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13
Q

How do you look at a histogram and find the median

A
  1. write the values on the graph
  2. Add them up
  3. +1
  4. divided by 2
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14
Q

Which measure of center is NOT resistant to outliers- Median or Mean?

A

The Mean

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15
Q

What does the z score measure?

A

whether the data value is above or below average in standard deviations

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16
Q

What is the symbol for correlation

A

r

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17
Q

In a scatter plot- what does it mean when the data points are spread apart

A

r value further away from 1

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18
Q

What types of variables must you use to compute the r value

A

quantitative values

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19
Q

What do the regression line and the correlation have in common?

A

both have the same sign (neg or pos)

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20
Q

What is included in a 5 number summary

A
  1. Min
  2. IQ1
  3. Median
  4. IQ3
  5. Max
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21
Q

If the scatter plot is curved is the regression line and r value appropriate?

A

no

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22
Q

What are the 3 percentages affiliated with the empirical rule? (if histogram is bell shaped)

A

68

95

99.7

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23
Q

How many standard deviations is 68% away from the mean?

A

1

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24
Q

How many standard deviations is 95% away from the mean?

A

2

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25
Q

How many standard deviations is 99.7% away from the mean?

A

3

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26
Q

What is the formula for the z score?

A

individual- pop mean / standard deviation

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27
Q

What is the value you get in the z-score mean

A

it is the number of standard deviations= correspons with the s.d. value

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28
Q

What are the steps to determine an outlier?

A
  1. IQR x 1.5
  2. Add that value to Q3
  3. Add value to Q1
  4. Evaluate new range and compare
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29
Q

What must you do before graphing a box plot?

A

determine if there are any outliers

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30
Q

In terms of scatter plot, what does bivariate mean?

A

2 quantitative variables being compared

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31
Q

Which value is the slope b0 or b1?

A

b1

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32
Q

How do you compute the y-intercept?

A

b0= yavg- ( b1 * xavg)

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33
Q

What tables do you need to get the sum for b1?

A

x, y, x - xavg, y - yavg, x - xavg2, y - yavg2

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34
Q

Sxy/Sxx

A
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35
Q

In the error sum of squares what new value are you computing?

A

the comparison of y actual and y with the equation

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36
Q

What does r2 measure

A

the percent of variation explained by observed values in response to the regression

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37
Q

the total sum of squares

A

is the total sum of variation in the response variable.

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38
Q

SSR or regression sum of squares

A

the variation explained by the regression

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39
Q

What indicates a strong linear relationship of r

A

value close to -1 or 1

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40
Q

Define a random experiment

A

an action whose outcome cannot be predicted with certainity. Each subject equally likely.

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41
Q

Define a sample space

A

the collection of all possible outcomes for an experiment

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42
Q

Define an Event

A

a collection of outcomes. A subset of a sample space.

43
Q

Define mutually exclusive

A

2 or more events, no 2 having anything in common

44
Q

Define independent events

A

may still have something in common, but does not affect the probability of the former event.

45
Q

Define the complement of an event

A

1- the probability the evend does not occur. Not A

46
Q

Descrime the union of 2 events

A

A can occur B can occur or Both can occur

47
Q

What is the intersection of 2 events

A

A and B occur simultaneously

48
Q

P(A) = 1 means..

A

the event is certain to happen

49
Q

P(A) = 0 neabs

A

the event will NOT happen

50
Q

What rule does this equation fall under:

P(A or B) = P(A) + P(B)

A

Special Addition for mutually exclusive events

51
Q

The complementation rule formula

A

P(A) = 1 - P(not A)

52
Q

What rule does this equation fall under:

P(A or B) = P(A) + P(B) - P(A + B)

A

General Addition Rule. Because it will always get you the right answer

53
Q

What is a contingency table?

A
  • the distribution of one variable in rows another in columns
  • study the association between the two variables
54
Q

the probability of one event occuring when it’s known that another one has occurred.

A

Conditional Probability

55
Q

Finish the equation P ( B | A)=

A

P(A & B) / P(A). (Pay attention to the sample size.) General Conditional Rule.

56
Q

When referring to the intersection of 2 events, What is the general rule?

A

P(A & B) = P(A) * P (B | A)

57
Q

What is the special conditional rule-

A

When A & B are independent events. P(B | A) = P(B)

58
Q

When referring to the union of 2 events. What is the special rule for independent events

A

P( A & B) = P(B) * P(A)

59
Q

What is a random variable?

A

a numerical value that’s determined by chance

60
Q

Define the probability distribution

A

the probabilities with which X takes those values

61
Q

How to remember greater than and less than….

A

the pointy end is facing the smaller one ex 9 >6

62
Q

When reading the equation, decide which formula to use before you plug in the equation

A
63
Q

If two events are mutually exclusive, what is their probability?

A

0

64
Q

If two events are independent what is the probabilty?

A

you must multiply them

65
Q

Suppose E and F are 2 mutually exclusive event, with P(E)=0.4 and P(F)=0.2 then P(E or F) equals..

A

0.6

66
Q

How would you write 5% of students who work full time are full time student

A

P(S|W) = 0.05

67
Q

How do you explain in words when 2 events are dependent

A

P(S|W) does NOT equal P(S)

68
Q

What would a venn diagram look like if Student A skips class and Student B does not skip class

A
69
Q
A
70
Q

What is the proportion formula for Z in terms of confidence interval

A

P(1 - P)/N, then SQUARE ROOT

71
Q

Where does a density curve lie on a graph

A

the x axis

72
Q

What is the total area under a curve?

A

1

73
Q

What is a continuous probability distribution?

A

a density curve

74
Q

How do you find the probability association with a normal distribution

A
  • z = x - µ / σ
  • then use the Table II
75
Q

What is a percentile?

A

Solve for X “unstandardize”

x= µ + zσ

76
Q

Define statistic

A

the value of a statistic will vary from one random sample to the next

77
Q

If the x variable follow a normal distribution with µ and σ, then which rule applies?

A

68 - 95 - 99.7 %

78
Q

Parameter

A

the value of a parameter remains constant

79
Q

Define Sampling Error

A
  • Because statistics are random variables
  • a slight error associated with the estimate
  • x - u
80
Q

What is a sampling distribution

A
  • a probability distribution for all possible samples
81
Q

If the sample is from a normal poulation then what does x bar have?

A

a normal sampling distribution

82
Q

What is σx?

A

= σ / square rt of n

83
Q

How are probabilities found?

A

standardizing using the standard normal table

84
Q

How are percentiles found?

A

by unstandardizing from the standard normal table

85
Q

Define the Central Limit Theorem

A
  • when the sample size n is large is a normal distribution
86
Q

Define a point estimate?

A
  • single number estimate
  • give no indication of the size of the sampling error
87
Q

Will the point estimate equal the true value?

A

No, because of sampling error

88
Q

What does the margine of error indicate

A

how big the sampling error might be

89
Q

What is a confidence interval?

A

a range of estimate for the true population parameter.

= Point Estimate +/- Margin of Error

90
Q

What does level of confidence mean?

A

how certain we can be that the true value is contained in the interval (%)

91
Q

What also increases as the level of confidence increases?

A

the width of the confidence interval

92
Q

What happens to the width of the confidence interval when n increases?

A

the width decreases

93
Q

If you are given the endpoints of a confidenct interval, how do you calculate the mean?

A

add and divide by 2

94
Q

What weight sparates the value of the heaviest 10% al all books from the 90% (90th percentile) what type of question is this?

A

unstandardizing- look for Z in table II

95
Q

If you are given *n * in a problem with mean and standard deviation, what is the first thing you need to do?

A
  1. convert σ to σx
  2. use z equation
  3. look up in table II
96
Q

which equation do you use to obtain the confidence interval?

A

t-interval ch 8

97
Q

When looking for a proportion, where can you find the equation?

A

Chapter 12- “z-interval for p”

98
Q

For a hypothesis test, if the question says the words “true mean” which equation do you use?

A
99
Q

When the equation says not equal what do you need to do?

A
  • multiply T x 2, if its comparing u
  • multiply P x 2, if it comparing 2 u values
100
Q

If the P value is less than alpha what does that mean?

A
101
Q

The greater the t value means

A
102
Q

If the p value is greater than alpha, what does this mean?

A
103
Q

if your using the t-interval for u. what do you do to finish the formula?

A

look up t value in table iv

104
Q

when do you use the t-interval for u equation

A

when you do not know sigma (standard deviation)

Summer 2014 (6 decks)

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