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STRAIGHTERLINE INTRODUCTION TO STATISTICS EXAM QUESTIONS AND ANSWERS
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STRAIGHTERLINE INTRODUCTION TO STATISTICS EXAM QUESTIONS AND ANSWERS
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STRAIGHTERLINE INTRODUCTION TOSTATISTICS EXAM QUESTIONS AND
ANSWERS
Simpson's paradox - Answer-When a lurking variable causes you to rethink the direction
of an association
Probability sampling plan - Answer-any sampling plan that relies on random selection
(avoids bias).
Simple Random Sampling - Answer-Every member of the population has an equal
probability of being selected for the sample
Cluster Sampling - Answer-Used when the population is naturally divided into groups.
Take a random sample of clusters and use all individuals within those clusters as the
sample.
Stratified sampling - Answer-Used when the population is naturally divided into sub-
populations called stratum. Choose a simple random sample from each stratum and use
these together as the sample.
Multistage sampling - Answer-a probability sampling technique involving at least two
stages: a random sample of clusters followed by a random sample of people within the
selected clusters
Observational study - Answer-values of the variable or variables of interest are recorded
as they naturally occur; no interference
Sample surveys - Answer-a particular type of observational study in which individuals
report variables' values themselves, frequently by giving their opinions.
Experiment - Answer-researchers "take control" of the values of the explanatory
variable because they want to see how changes in the value of the explanatory variable
affect the response variable
The Complement Rule - Answer-P(not A) = 1 - P(A)
useful for finding events of the type "at least one of..."
General Addition Rule - Answer-P(A or B) = P(A) + P(B) - P(A and B)
used to find events of the type events of the type "A or B"
General Multiplication Rule - Answer-P(A and B) = P(A) * P(B | A)
, Used for events of the type "A and B"
or when A and B are independent:
P(A and B) = P(A) * P(B)
Conditional probability
P(B | A) - Answer-the conditional probability of event B occurring given that event A has
occurred
P(B | A) = P(A and B) / P(A).
Methods for checking for independence of two variables - Answer-If the two variables
are independent:
· P(A|B)= P(A)
· P(B|A)=P(B)
· P(B|A)=P(B| not A)
· P(A and B)= P(A) * P(B)
1. Discrete random variable
2. Continuous random variable - Answer-1. things we count
2. things we measure
Probability distribution - Answer-a list of a variable's possible values and their
corresponding probabilities
Center of a random variable distribution is measured by its - Answer-mean
Spread of a random variable distribution is measured by its - Answer-variance or
standard deviation
Rules for the linear transformation of one random variable - Answer-μ(a+b)X=a+b μX
σ^2a+bX=b^2σ^2X
1. Usual
2. Unusual - Answer-1. Within two standards deviations of the mean
2. More than two standard deviations above or below the mean
Binomial Experiment - Answer-1. a fixed number of trials (notation: n trials)
2. each trial must be independent of the others
3. each trial has two possible outcomes, called "success" (the outcome of interest) and
"failure"
4. there is a constant probability (p) of success for each trial, the complement of which
is the probability (1 - p) of failure
Binomials
The Number of outcomes with x successes out of n trials (formula) - Answer-[n!]/[x!*(n-
x)!]
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