Sampling Methods
Standing in front of a mall and asking people to answer questions for your research
Convenience Sampling
I want to estimate the proportion of people in Chula Vista who own cats. I stand outside a local pet store and ask every 4th person whether they own a cat or not. What is the most prominent kind of bias evident?
Undercoverage
What does r= -.73 tell you about the correlation?
There's a strong, negative linear association between variables
What is the mean and standard deviation of a standard Normal distribution?
mean=0
standard deviation=1
What percentile corresponds to Q3, the third quartile?
75th percentile
I want to estimate the proportion of people in Chula Vista who own cats. I stand outside a local pet store and ask every 4th person whether they own a cat or not. What kind of sampling procedure is this?
Systematic Sampling
In Fall 1995, the BBC in Britain requested viewers to call the network and indicate their favorite poem.
Voluntary Response
You would look at this plot to check to see whether a linear regression is appropriate.
Residual plot
You are told that your score on an exam is at the 85th percentile of the distribution of scores. This means that...
Your score higher than approximately 85% of the people who took this exam.
When an individual is selected to be in a sample but chooses not to participate or cannot be reached
Nonresponse
Farmer Joe separates his apple tree farm into 10 regions. He counts the number of apples produced in just one of the regions and uses that estimate to predict the number of apples produced on the whole farm. This is _______ sampling.
Cluster Sampling
“Some cell phone users have developed brain cancer. Should all cell phones come with a warning label explaining the danger of using cell phones?”
What kind of bias is evident in this survey question?
Response Bias
You would look at this plot to check to see whether a linear regression is appropriate.
Extrapolation
In a normal distibution, what percent of the data falls within 1.3 standard deviation of the mean?
0.8064
How do you describe a distribution?
Shape, outliers, center and variability
This sample is selected by dividing the population into subgroups and then taking a fixed number of units from each group using the simple random sample.
Stratified Sampling
WVHS decided to perform Beauty and the Beast. They wonder if the community likes their performance. They select a simple reandom sample of 200 attendees and send an email to each of them asking if they like the performance or didn't like the performance. Only 42 attendees responded.
Name the type of bias.
Non-response
A new process designed to increase the temperature inside steel girders shows great promise. Using an initial temperature (degree C), we can predict the final temperature (degree C). The equation has a y-intercept of 37. Interpret the value.
There's a predicted final temperature of 37 degrees C, when the initial temperature is 0 degrees C.
The distribution of heights of adult of adult men is approximately Normal with mean 69 inches and standard deviation 2.5 inches. How tall is a man whose standardized height is -0.3?
68.25 inches
To the nearest tenth, the percentage of scores in a standard Normal distribution that are below z=-1.4 is...
8.1%
Select three female students and three male students to receive ice cream by putting all the men's names in one hat and all the women's names in a different hat and picking out three names from each hat.
Stratified Sampling
A store manager wants to estimate the proportion of all the customers of the store who would use store credit card for their purchases. The manager selects a random sample of 1000 customers from their customer loyalty program list and sends them a survey asking if they would be interested in applying for a store credit card. Seventy-eight customer respond to the survey. What kinds of biases are evident in this scenario?
Non-response and Undercoverage
A new process designed to increase the temperature inside steel girders shows great promise. Using an initial temperature (degree C), we can predict the final temperature (degree C) by using a slope of 1.095. Interpret that value.
For each additional degree in initial temperature there is a 1.095 degree predicted increase in final temperature.
SAT N(500, 100) ACT N(18, 6) The student scored a 720 on the SAT and 18 on the ACT. The score that is more appealing to universities...
SAT score
The sum of the data under the curve is equal to 1.
Density curve