Sampling Methods
Selecting respondents in no particular order is what kind of sampling?
Random sampling
A set of data with a mean of 45 and a standard deviation of 8.3 is normally distributed. What value is one standard deviation above the mean?
53.3
On a bell curve, what percentage of the data are BELOW the man?
50%
means
A probability distribution involving two random variables is called what?
A bivariate probability distribution.
Ordering the population and then selecting from it at regular intervals is what kind of sampling?
Systematic sampling
A set of data with a mean of 45 and a standard deviation of 8.3 is normally distributed. What value is one standard deviation below the mean?
36.7
A normal distribution of scores has a standard deviation of 10. Find the z-score of an item 20 points above the mean.
2
In 2018, the Amazon Alexa app was downloaded some 2800 times per day from the Google Play Store. Assume that the number of downloads per day from Google Play are normally distributed with a mean of 2800 and a standard deviation of 860.
What is the probability there are between 1500 and 2500 downloads a day?
What standard deviation should you use to answer this question (write the number)?
860
Suppose that historical sales records indicate that 40% of all customers who enter the department store make a purchase. What is the probability that two of the next three customers will make a purchase?
Identify n, x, and p.
n=3
x=2
p = .40
A type of survey where the person most knowledgeable on the subject of the study selects elements of the population that he or she feels are most representative of the population is using what kind of sampling?
Judgement sampling
A machine is used to put bolts into boxes. It does so such that the actual number of bolts in a box is normally distributed with a mean of 106 and a standard deviation of 2. What percentage of boxes contain more than 104 bolts?
84%
A normal distribution of scores has a standard deviation of 10. Find the z-scores corresponding to a value 35 points below the mean.
-3.5
Sales at a clothing chain are currently running at an annual rate of $310 per square foot. You have been asked by management to conduct a study of 27 locations. Assume the standard deviation in annual sales per square foot for the population of all 575 store locations is $76.
What is the expected value of x bar?
$310
f(x) x
.2 50
.5 30
.3 40
Given these data, what is the expected value of x?
37
A type of survey that divides a population into subpopulations, like their ZIP code, and then picks people randomly from a particular subgroup for the survey or experiment is what kind of sampling?
Cluster sampling
A machine is used to put bolts into boxes. It does so such that the actual number of bolts in a box is normally distributed with a mean of 106 and a standard deviation of 2. What percentage of boxes contain between 102 and 112 bolts?
97.5
On a statistics test the class mean was 63 and the standard deviation was 7, on a biology test the class mean was 23 and has a standard deviation of 3.9. Find the z-score of a grade of 60 in statistics and 20 on the biology test.
-.43 and -.77
In a sample of 30 respondents to a questionnaire about school quality, 72 percent said they were "very satisfied" with their schools.
What is the standard error of this sample?
.082
Find the z-score given: ยต=30, Sx= 5, and x =39.
1.8
A type of survey that divides a population into groups, like their age, and then picks people randomly from a particular group for the survey or experiment is what kind of sampling?
Stratified sampling
The mean of a normally distributed set of data is 52 and the standard deviation is 4. Approximately 95% of all the cases will lie between which measures?
44-60
On a statistics test the class mean was 63 and the standard deviation was 7, on a biology test the class mean was 23 and has a standard deviation of 3.9. Find the z-score of a grade of 60 in statistics and 20 on the biology test. Which grade was better relative to other?
Statistics
Sales at a sunglasses chain are currently running at an annual rate of $222 per square foot. Assume the standard deviation in annual sales per square foot for the population of all 7 store locations is $11.
At what amount per square foot would you consider a store to be especially low-performing (an outlier)?
To calculate the probability in a uniform probability distribution, a = __?
base*height