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Research MethodologyAnswered question
Zackary Duffy Zackary Duffy 2022-09-11

A survey has been conducted to see how many people in a town of 40,000 people used Ebay to purchase a product last year. A simple random sample of 230 is taken and from this sample 52 people had used Ebay last year.
I'm asked to estimate the total number of people who used Ebay last year and compute the 95% confidence interval for the total (we are allowed to assum the 97.5% quantile of the normal distribution is 1.96).
The first part I believe is straightforward, I just find my ratio R and multiply by my population total t to get 52/230⋅40,000=9043.4783 ( t ^ ) but finding the confidence interval is a bit confusing because I'm hardly given any information here. I have formulas I would usually use to find the variance of R and then the variance of t ^ and then find the confidence interval but all these formulas either require y ¯ (and sometimes x ¯ ) or they require y i 2 , y i x i , x i 2 and I have none of these. I only have the total population, the sample size and the ratio. Any ideas how I would obtain my 95% confidence interval for the total?
Also, there is a second part that asks what sample size would be required for the total number to be within 940 units of the true value (I'm guessing they mean the total number of people in the town who used ebay last year), with confidence 95%? On this part of the question I'm just not sure what to do.
These are both low mark questions so I'm probably just forgetting a formula or missing something but I just can't see a way to get my answers with so little information given. I've double and triple checked and this is for sure the only information that is given about this survey.

Research MethodologyAnswered question
Deacon House Deacon House 2022-09-10

Is there a way to test the "accuracy of a binomial survey"?
I've been away from mathematics for a while and forgotten almost everything. It doesn't come from a text book; I was given an assignment in my training for a job and wondered if I can use my mathematical knowledge. All I have to do is actually interpret the data and say "more than 50 percent of the people surveyed thinks "yes" to the question" but I'm taking a step further and trying to say how "accurate" is the result? Basically, here's what I am given
There's a supermarket that is experiencing a fall in revenues. A survey was conducted and it asked whether "the customer thinks the workers are unfriendly/unhelpful." out of a 100 randomly chosen customers on the same day (100 different customers) 51% answered "yes."
However, the total number of customers that visited the supermarket is expected to be around 485. The total that visited the supermarket that month is 19700. How confident are we to say that more than 50% are not happy with the workers among all of those who visited the store a. that day b. that month?
I vaguely recalled Chi-squared ad z-test but I wasn't so sure; I tried the z-test with
z = p π π ( 1 π ) n
where p=0.51,π=0.5,n=100. Thing is, I get z=0.2 and the z table seems to tell me this is a very inaccurate result. In any case, my data and the question I ultimately want to answer is as above. Along the process of doing so, if no one would want to actually show me how to do this, can you please answer
What's the most apt test to answer a question like this? And why?
I think, as people start writing some answers, my senses will come back, some words and terms ringing a bell, reminding me of certain formulas, rules etc.

Surveys are a useful way to get feedback from customers and the questions you ask are important. There are three main types of survey questions: closed-ended, open-ended, and rating-scale. Closed-ended questions provide specific answers, open-ended questions are more open-ended, and rating-scale questions are numerical. It's important to use the right type of question so that customers can easily provide the answers you are looking for. Equations can also be used to help determine the answers to survey questions and help you make better decisions. With the right survey questions and equations, you can get the information you need to make informed decisions.