What is the margin of error for the sample mean at a 95% confidence level? Hint: Look at the notes given above to see how the margin of error is computed.  2. Will the margin of error increase/decrease if 200 delinquent credit cards were sampled instead of 100? Why? Hint: Look at the notes given above to see how the margin of error is computed and how the sample size n impacts its value.  3. Give a 95% confidence interval for the mean amount owed on all delinquent credit card accounts for this bank (i.e. population mean µ). Hint: Look at the notes given above to see how the confidence interval for the population mean is computed.

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A bank took a sample of 100 of its delinquent credit card accounts and found that the mean owed on these accounts was $2,130. It is known that the standard deviation for all delinquent credit card accounts at this bank is $578.

(Hint: First write out the values for n, x¯, and σ)

1. What is the margin of error for the sample mean at a 95% confidence level? Hint: Look at the notes given above to see how the margin of error is computed. 

2. Will the margin of error increase/decrease if 200 delinquent credit cards were sampled instead of 100? Why? Hint: Look at the notes given above to see how the margin of error is computed and how the sample size n impacts its value. 

3. Give a 95% confidence interval for the mean amount owed on all delinquent credit card accounts for this bank (i.e. population mean µ). Hint: Look at the notes given above to see how the confidence interval for the population mean is computed. 

4. Will the confidence interval become wider or narrower if 200 delinquent credit cards were sampled instead of 100? Why? Hint: Look at the notes given above to see how the confidence interval is computed and how the sample size n impacts its lower and upper bounds and hence the width. 

5. Will the confidence interval become wider or narrower if the sample size is still 100 but the confidence level is increased from 95% to 99%? Why?

Hint: Look at the notes given above to see how the confidence interval is computed and how the multiplier depends on confidence level i.e. z∗ impacts its lower and upper bounds and hence the width.

 

A population mean is the numerical average of a variable in the entire population of interest. One example would be the average amount spent o
dairy products by adult Americans in the previous year. The actual numerical value of a population mean would rarely be known.
A sample mean is the numerical average of the data for a variable in a sample. One example would be the average amount spent on dairy product
in the previous year by the respondents to a sample survey. The value of the sample mean might be used to estimate an unknown population
mean.
The Standard Error of a sample Mean (often abbreviated S.E.M.) is the standard deviation of the sampling distribution of a sample mean. In a
random sample, it is estimated by (the sample standard deviation divided by the square root of the sample size).
Chapter 5 discusses the likelihood of observing sample means in a specific range from a population with a known mean and standard deviation.
Conclude
What does our knowledge of
the parameter values tell us
about the population?
Parameters
Inference
We want to infer what parameter
values are most consistent with
the sample statistic at han
Population
STATISTICAL
PARADIGM
Statistical Summaries
and Pictures
Probability
The rules of probability tell us
the likelihood of different types
of samples that might arise from
a particular population.
Samples
Describe and Compare
Data is collected from the samples
and, with sample data in hand, we
attempt to create statistical
summaries and pictures that give the
salient features of the data collected.
Transcribed Image Text:A population mean is the numerical average of a variable in the entire population of interest. One example would be the average amount spent o dairy products by adult Americans in the previous year. The actual numerical value of a population mean would rarely be known. A sample mean is the numerical average of the data for a variable in a sample. One example would be the average amount spent on dairy product in the previous year by the respondents to a sample survey. The value of the sample mean might be used to estimate an unknown population mean. The Standard Error of a sample Mean (often abbreviated S.E.M.) is the standard deviation of the sampling distribution of a sample mean. In a random sample, it is estimated by (the sample standard deviation divided by the square root of the sample size). Chapter 5 discusses the likelihood of observing sample means in a specific range from a population with a known mean and standard deviation. Conclude What does our knowledge of the parameter values tell us about the population? Parameters Inference We want to infer what parameter values are most consistent with the sample statistic at han Population STATISTICAL PARADIGM Statistical Summaries and Pictures Probability The rules of probability tell us the likelihood of different types of samples that might arise from a particular population. Samples Describe and Compare Data is collected from the samples and, with sample data in hand, we attempt to create statistical summaries and pictures that give the salient features of the data collected.
Confidence Intervals for a population mean (n ≥) 30
For large random samples, a confidence interval for a population mean is given by
sample mean ±ME(sample mean) = sample mean ± z*SE(sample mean) = sample mean ±(z*vñ)
where z* is a multiplier number that comes from the normal curve and determines the level of confidence.
Multiplier Number (z*)
3.0
2.58 (2.576)
2.0 (more precisely 1.96)
1.645
1.282
1.15
1.0
Level of Confidence
99.7%
99%
95%
90%
80%
75%
68%
Transcribed Image Text:Confidence Intervals for a population mean (n ≥) 30 For large random samples, a confidence interval for a population mean is given by sample mean ±ME(sample mean) = sample mean ± z*SE(sample mean) = sample mean ±(z*vñ) where z* is a multiplier number that comes from the normal curve and determines the level of confidence. Multiplier Number (z*) 3.0 2.58 (2.576) 2.0 (more precisely 1.96) 1.645 1.282 1.15 1.0 Level of Confidence 99.7% 99% 95% 90% 80% 75% 68%
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