Econ 2843 Exam 2 Review Brent Norwood Questions
And Answers 100% Pass
what is z score - ANSWER how much a value differs from the standard deviation
Z score formula - ANSWER (x-u)/
(ô/√n)
What is a continuous random variable - ANSWER a variable that cannot be counted, but
is found from measuring (ex: height, weight, temperature)
has a probability density function
what is the probability that a continuous random variable assumes a value - ANSWER 0
what is a discrete random variable - ANSWER a countable number of values (ex: number
of girls in class)
has a probability mass function
confidence interval excel code to find probability - ANSWER < = NORM.DIST
> = 1-NORM>DIST
confidence interval excel code to find x to reach a given probability - ANSWER < =
NORM.INV
> = 1-NORM.INV
if lambda=4 what is the expected value - ANSWER 1/4 ->.25
Standard Deviation Formula - ANSWER = (√(b-a)^2/12)
If given 2 end data points 40 and 300 what is the expected mean and standard deviation
- ANSWER mean= 170
St dev= 75.1
What is the probability that any random number is more or less than the mean - ANSWER
50%
empirical rule - ANSWER 1 standard deviation away from the mean is 67%
2 standard deviations away is 95%
3 standard deviations away is 99.9%
, the probability variable assumes a value with an interval P(a<x<b) is defined as -
ANSWER the shaded area
you find the probability greater than a point by finding the probability and doing what -
ANSWER subtracting it from 1
What is selection bias - ANSWER choosing people that would skew results (surveying
only ou students based on what the best college is)
Nonresponse Bias - ANSWER when people do not answer the questions (teacher
surveys)
social desirability bias - ANSWER when people respond to questions based on what they
SHOULD say
what is the relationship between expected value of the sample mean and population
mean - ANSWER expected value of the sample mean = the expected value of the
population = mean
E(X)=E(x)=u
what is the central limit theorem - ANSWER n>=30
sample sizes greater than or equal to 30 are sufficient for the CLT to hold
- larger sample size is better because it decreases margin of error and standard error
when is sampling distribution of P considered normal? - ANSWER when p>=5 and
(1-p)>=5
what happens as sample size gets larger - ANSWER - distribution becomes more
normally distributed
- standard error decreases
- Margin of error decreases
- confidence interval gets wider
- T distribution begins to look more like Z distribution (gets taller and thinner)
what conditions must be met regarding qualitative data and the population/sample
proportion - ANSWER it is important to have only one population, but many samples can
be drawn from it
if you do not have a set upper and lower limit for statistical quality control, what is the
general rule to find them - ANSWER (3 x standard deviation)+- mean
how can you find the sample proportion - ANSWER x/n
if 30 people have dogs out of a sample of 100, what is the sample proportion? - ANSWER
And Answers 100% Pass
what is z score - ANSWER how much a value differs from the standard deviation
Z score formula - ANSWER (x-u)/
(ô/√n)
What is a continuous random variable - ANSWER a variable that cannot be counted, but
is found from measuring (ex: height, weight, temperature)
has a probability density function
what is the probability that a continuous random variable assumes a value - ANSWER 0
what is a discrete random variable - ANSWER a countable number of values (ex: number
of girls in class)
has a probability mass function
confidence interval excel code to find probability - ANSWER < = NORM.DIST
> = 1-NORM>DIST
confidence interval excel code to find x to reach a given probability - ANSWER < =
NORM.INV
> = 1-NORM.INV
if lambda=4 what is the expected value - ANSWER 1/4 ->.25
Standard Deviation Formula - ANSWER = (√(b-a)^2/12)
If given 2 end data points 40 and 300 what is the expected mean and standard deviation
- ANSWER mean= 170
St dev= 75.1
What is the probability that any random number is more or less than the mean - ANSWER
50%
empirical rule - ANSWER 1 standard deviation away from the mean is 67%
2 standard deviations away is 95%
3 standard deviations away is 99.9%
, the probability variable assumes a value with an interval P(a<x<b) is defined as -
ANSWER the shaded area
you find the probability greater than a point by finding the probability and doing what -
ANSWER subtracting it from 1
What is selection bias - ANSWER choosing people that would skew results (surveying
only ou students based on what the best college is)
Nonresponse Bias - ANSWER when people do not answer the questions (teacher
surveys)
social desirability bias - ANSWER when people respond to questions based on what they
SHOULD say
what is the relationship between expected value of the sample mean and population
mean - ANSWER expected value of the sample mean = the expected value of the
population = mean
E(X)=E(x)=u
what is the central limit theorem - ANSWER n>=30
sample sizes greater than or equal to 30 are sufficient for the CLT to hold
- larger sample size is better because it decreases margin of error and standard error
when is sampling distribution of P considered normal? - ANSWER when p>=5 and
(1-p)>=5
what happens as sample size gets larger - ANSWER - distribution becomes more
normally distributed
- standard error decreases
- Margin of error decreases
- confidence interval gets wider
- T distribution begins to look more like Z distribution (gets taller and thinner)
what conditions must be met regarding qualitative data and the population/sample
proportion - ANSWER it is important to have only one population, but many samples can
be drawn from it
if you do not have a set upper and lower limit for statistical quality control, what is the
general rule to find them - ANSWER (3 x standard deviation)+- mean
how can you find the sample proportion - ANSWER x/n
if 30 people have dogs out of a sample of 100, what is the sample proportion? - ANSWER
