Inferential Statistics Bias in Studies
Inferential Statistics
Bias in Studies
Choose EITHER Option A or Option B for your initial post. Please respond to two or more of the posts by Sunday night. At least one of those responses should be to a person who picked a different option than you did.
Option A:
A survey is conducted to determine the proportion of young adults who earn less than $15,000. Two sampling methods are being considered. Method A involves standing on a downtown street corner and randomly picking several young adults to interview every 10 minutes during a 12-hour period. Method B involves posting the question on several popular young adult Websites; the viewer simply has to click on one of two possible answers to participate.
State a possible source of bias for Method A, and describe how it may affect the results.
State a possible source of bias for Method B, and describe how it may affect the results.
Option B:
Does cell phone radiation increase a person’s risk of getting cancer? How can an observational study be performed?
MAT308 Inferential Statistics
Week 3 Discussion
Sampling Distributions for Means
Make a copy of Sampling Distribution for Means download. After completing the activity copy and past your answer from #9 in this week’s discussion post. Please also attach your copy of the entire activity.
MAT308 Name:________________________
Investigation
Sampling Distributions of
Objectives
In this activity, you will use the applet for investigating the sampling distribution of . You will use the applet to explore the shape of the sampling distribution when the population is normally distributed and when the population is not normal.
Materials
Computer with internet access – one per student or pair of students.
Launch the Sampling Distributions applet at http://onlinestatbook.com/stat_sim/sampling_dist/index.html. When the BEGIN button appears on the left side of the screen, click on it. You will see a yellow page entitled “Sampling Distributions”.
1. There are choices for the population distribution: Normal, uniform, skewed, and custom. The default is Normal. Click the “Animated” button.
? What happens?
? Click the button several more times. What do the black boxes represent?
? What is the blue square that drops down onto the plot below?
? What does the red horizontal band under the population histogram tell us?
Notice the left panel. Important numbers are displayed there. Did you notice that the colors of the numbers match up with the objects to the right? As you make things happen, the numbers change accordingly, like an automatic scorekeeper.
2. Click on “Clear lower 3” to start clean. Then click on the “10,000” button one time under “Sample;” to simulate taking 10,000 SRSs of size n = 5 from the population. Answer these questions:
? Does the approximate sampling distribution (blue bars) have a recognizable shape? Click the box next to “Fit normal.”
? Compare the mean of the approximate sampling distribution with the mean of the population.
? How is the standard deviation of the approximate sampling distribution related to the standard deviation of the population?
3. Click “Clear lower 3.” Use the drop-down menus to set up the bottom graph to display the mean for samples for size n = 20. Then sample 10,000 times. How do the two distributions of compare: shape, center, spread?
4. What have you learned about the shape of the sampling distribution of when the population has a Normal shape?
5. Now select “Skewed population. Set the bottom two graphs to display the mean—one for samples of size 2 and the other for samples of size 5. Click the Animated button a few times to be sure you see what’s happening. Then “Clear lower 3” and take 10,000 SRSs. Describe what you see.
6. Change the sample sizes to n = 10 and n = 16 and repeat Step 1. What do you notice?
7. Now change the sample sizes to n = 20 and n = 25 and take 10,000 more samples. Did this confirm what you saw in Step 2?
8. Clear the page and select “Custom” distribution. Click on a point on the population graph to insert a bar of that height. Or click on a point on the horizontal axis and drag up to define a bar. Make a distribution that looks as strange as you can. (Note: You can shorten a bar or get rid of it completely by clicking on the top of the bar and dragging down to the axis.) Then repeat #5 – 7 for your custom distribution.
? Step 1: Set the bottom two graphs to display the mean—one for samples of size 2 and the other for samples of size 5. Click the Animated button a few times to be sure you see what’s happening. Then “Clear lower 3” and take 10,000 SRSs. Describe what you see.
? Step 2: Change the sample sizes to n = 10 and n = 16 and repeat Step 1. What do you notice?
? Step 3: Now change the sample size to n = 20 and n = 25 and take 10,000 more samples. Did this confirm what you saw in Step 2?
9. Summarize what you learned about the shape of the sampling distribution of .
MAT308 Inferential Statistics
Week 4 Discussion
Normal Distribution
Suppose that in a large class, the instructor announces that the average grade on an exam is 75. Which is more likely to be closer to 75:
The exam grade of a randomly selected student in the class?
OR
The mean exam grade of a sample of 10 students?
Explain.
MAT308 Inferential Statistics
Week 6 Discussion
Confidential Intervals
Please go to the fish tutorial website (Links to an external site.) and follow the instructions for the tutorial. (The tutorial button is located in the lower middle of the screen.) Then answer the following questions:
How did the applet visually show the confidence interval and the point estimate for the population mean?
How did the applet visually show a confidence interval that did NOT capture the population mean? How often would we expect this to occur?
What happened to the confidence intervals when the level of confidence increased to 99%?
What happened to the confidence intervals when the sample size was increased to 40?
5. Did the applet help you understand what confidence intervals are? In your own words, what are confidence intervals?
MAT308 Inferential Statistics
Week 7 Discussion
Hypothesis Test One Proportion
This discussion board post has 3 parts.
Use your textbook or google to find a problem for a hypothesis test for one proportion such as the one below. (It is the same one as the introduction) Make sure to post your problem no later than 11:59 on Wednesday night. Make sure you solve your own problem this week…you will need the information for next week)
Pick another student’s problem and solve it. Make sure to include your null and alternative hypothesis, your test statistic, your p-value, decision, and conclusion in the context in your response. (If someone has already replied to the problem then please pick a different one. If we have an odd number or if one is not replied to by Sunday night, I will post a response…I don’t promise it will be the correct response.)
During Reading Week, go back and respond to the person who worked on your problem. Let them know if they got it correct and if they didn’t let them know what the correct answer is.
How cool is Facebook? In a recent GenX2Z American College Student Survey, 90% of female college students rated the social network site Facebook as “cool.” The other 10% rated it as “lame.” Assume that the survey was based on a sample of 500 students. A marketing executive at Facebook wants to advertise the site with the slogan “More than 85% of female college students think Facebook is cool.” Can he conclude that the proportion of female college students who think Facebook is cool is greater than 0.85?
MAT308 Inferential Statistics
Week 10 Discussion
Project Proposal
Please post your project proposal (the same one that you submitted through Canvas Last week) to the discussion board by Wednesday night at 11:59.
During the week come back and read 1 student’s project proposal. Use the rubric to assess the proposal.
Creating a Webcam Video (Links to an external site.) or Screencast (Links to an external site.) that provides positive feedback and thought-provoking questions that will help them improve their project. Need help? Visit the Kaltura Media Tools Page (Links to an external site.)
To ensure that everyone receives some feedback from their peers, please do not respond to a proposal if someone else already has.
(Remember, you already submitted your proposal in Canvas last week so it should be ready to post in the discussion board.)
MAT308 Inferential Statistics
Week 13 Discussion
Choose EITHER Option A or Option B for your initial post. Please respond to two or more of the posts by Sunday night. At least one of those responses should be to a person who picked a different option than you did.
Option A:
An SRS of apartment listings in a large northeastern city comparing monthly rent ($) versus size (?ft?^2) yields following computer output:
Is a linear model appropriate for these data?Explain
Interpret the slope of the regression line.?^?
Interpret r^2 in context.
Option B: The calories and sugar content per serving size of ten brands of breakfast cereal are fitted with a least squares regression line with computer outputs:
Collepals.com Plagiarism Free Papers
Are you looking for custom essay writing service or even dissertation writing services? Just request for our write my paper service, and we'll match you with the best essay writer in your subject! With an exceptional team of professional academic experts in a wide range of subjects, we can guarantee you an unrivaled quality of custom-written papers.
Get ZERO PLAGIARISM, HUMAN WRITTEN ESSAYS
Why Hire Collepals.com writers to do your paper?
Quality- We are experienced and have access to ample research materials.
We write plagiarism Free Content
Confidential- We never share or sell your personal information to third parties.
Support-Chat with us today! We are always waiting to answer all your questions.
