A catalog sales company promises to deliver orders placed on the Internet within 3 days. Follow-up calls to a few randomly selected customers show that a 95% confidence interval for the proportion of all orders that arrive on time is 88 a) What does this mean? Are these conclusions correct? Explain. b) 95% of all random samples of customers will show that 88% of orders arrive on time. c) 95% of all random samples of customers will show that 82% to 94% of orders arrive on time. d) We are 95% sure that between 82% and 94% of the orders placed by the sampled customers arrived on time. e) On 95% of the days, between 82% and 94% of the orders will arrive on time.

A catalog sales company promises to deliver orders placed on the Internet within 3 days. Follow-up calls to a few randomly selected customers show that a 95% confidence interval for the proportion of all orders that arrive on time is 88 a) What does this mean? Are these conclusions correct? Explain. b) 95% of all random samples of customers will show that 88% of orders arrive on time. c) 95% of all random samples of customers will show that 82% to 94% of orders arrive on time. d) We are 95% sure that between 82% and 94% of the orders placed by the sampled customers arrived on time. e) On 95% of the days, between 82% and 94% of the orders will arrive on time.

Question
Confidence intervals
asked 2020-12-16
A catalog sales company promises to deliver orders placed on the Internet within 3 days. Follow-up calls to a few randomly selected customers show that a 95% confidence interval for the proportion of all orders that arrive on time is 88
a) What does this mean? Are these conclusions correct? Explain.
b) 95% of all random samples of customers will show that 88% of orders arrive on time.
c) 95% of all random samples of customers will show that 82% to 94% of orders arrive on time.
d) We are 95% sure that between 82% and 94% of the orders placed by the sampled customers arrived on time.
e) On 95% of the days, between 82% and 94% of the orders will arrive on time.

Answers (1)

2020-12-17
a) Incorrect. This implies certainty.
b) Incorrect. Different samples will give different results. Many fewer than 95% will have 88% on-time orders.
c) Incorrect. The interval is about the population proportion, not the sample proportion in different samples.
d) Incorrect. In this sample, we know 88% arrived on time
e) Incorrect. The interval is about the parameter, not about the days.
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Remember, the previous answer is only correct if the variables are Independent.
d) Now let's get the real percent that are Black and Unarmed by using the table?
If answer c is "significantly different" than answer d, then that means that there could be a different percentage of unarmed people being shot based on race. We will check this out later in the course.
Let's compare the percentage of unarmed shot for each race.
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If you compare answers d, e and f it shows the highest percentage of unarmed people being shot is most likely white.
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This is because there are more white people in the United States than any other race and therefore there are likely to be more white people in the table. Since there are more white people in the table, there most likely would be more white and unarmed people shot by police than any other race. This pulls the percentage of white and unarmed up. In addition, there most likely would be more white and armed shot by police. All the percentages for white people would be higher, because there are more white people. For example, the table contains very few Hispanic people, and the percentage of people in the table that were Hispanic and unarmed is the lowest percentage.
Think of it this way. If you went to a college that was 90% female and 10% male, then females would most likely have the highest percentage of A grades. They would also most likely have the highest percentage of B, C, D and F grades
The correct way to compare is "conditional probability". Conditional probability is getting the probability of something happening, given we are dealing with just the people in a particular group.
g) What percent of blacks shot and killed by police were unarmed?
h) What percent of whites shot and killed by police were unarmed?
i) What percent of Hispanics shot and killed by police were unarmed?
You can see by the answers to part g and h, that the percentage of blacks that were unarmed and killed by police is approximately twice that of whites that were unarmed and killed by police.
j) Why do you believe this is happening?
Do a search on the internet for reasons why blacks are more likely to be killed by police. Read a few articles on the topic. Write your response using the articles as references. Give the websites used in your response. Your answer should be several sentences long with at least one website listed. This part of this problem will be graded after the due date.
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