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Student Ages Suppose that 200 statistics students each took a random sample (with replacement) of 50 students at their college and recorded the ages of the students in their sample. Then each student used his or her data to calculate a \(95 \%\) confidence interval for the mean age of all students at the college. How many of the 200 intervals would you expect to capture the true population mean age, and how many would you expect not to capture the true population mean? Explain by showing your calculation.

Short Answer

Expert verified
It is expected that out of the 200 intervals, 190 would capture the true population mean age and 10 would not.

Step by step solution

01

Understand the Confidence Interval

A \(95\%\) confidence interval means that there is a \(95\%\) chance that the true population mean falls within the calculated range. Therefore, we expect that \(95\%\) of the samples taken will capture the true mean within their confidence intervals.
02

Calculate Intervals Capturing True Mean

To find out the number of intervals that would capture the true mean, multiply the number of intervals by the percentage of confidence intervals that contain the true mean. In this case, \(200\) samples times \(0.95\) (or \(95\%\)) equals \(190\). So, we would expect \(190\) of the \(200\) confidence intervals to contain the true population mean.
03

Calculate Intervals Not Capturing True Mean

The remaining \(5\%\) are expected not to capture the true mean. To determine this number, multiply the number of intervals by \(5\%\), or \(0.05\). In this case, \(200\) samples times \(0.05\) equals \(10\). So, we would expect \(10\) of the \(200\) confidence intervals not to contain the true population mean.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Population Mean
The population mean is a fundamental concept in statistics. It represents the average value of a particular characteristic in the entire population. In the context of the exercise, the population mean refers to the average age of all students at the college.
Calculating the population mean involves gathering data from the whole population, which is often impractical due to its large size. Instead, researchers use samples to estimate it.
The key reason for focusing on the population mean is to make inferences about the entire group based on limited data. With the help of statistical methods like confidence intervals, we can estimate the population mean with a certain level of confidence.
Sample Size
Sample size is the number of observations or data points collected from a population for statistical analysis. In scenarios like the described exercise, students took samples of size 50. This number plays a critical role in determining the accuracy and reliability of the estimation.
Larger sample sizes generally provide more accurate estimates of the population mean, reducing the margin of error. On the other hand, smaller sample sizes can lead to greater variability in the results, which might not reflect the true population mean efficiently.
When choosing a sample size, it's vital to find a balance. While larger samples lead to more precision, they also demand more resources. Thus, sample size is a crucial consideration in planning any statistical study.
Statistics Education
Statistics education equips students with the understanding of how data is collected, analyzed, and interpreted. It empowers them with the ability to make informed decisions based on data.
In the exercise, students applied their knowledge to calculate confidence intervals—an essential concept in statistics education. By analyzing samples, they learned how to make reliable inferences about a population.
Furthermore, statistics education emphasizes critical thinking, data literacy, and the application of statistical tools, which are invaluable skills in various fields. Through practical exercises like this, students gain hands-on experience that builds a lasting foundation in statistics.
Statistical Inference
Statistical inference involves making conclusions about a population based on data from a sample. It is a core aspect of the exercise, where students inferred information about the college's population mean age using sample data from their class.
Key methods of statistical inference include point estimation, interval estimation—as seen with confidence intervals—and hypothesis testing. Confidence intervals provide a range within which the true population parameter is expected to fall, giving a measure of reliability to the estimation.
Conclusions drawn from statistical inference are fundamental for decision-making in research and industry. By understanding the principles of statistical inference, individuals can appropriately interpret data outcomes and make meaningful conclusions.

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Most popular questions from this chapter

Female Height In the United States, the population mean height for 10 -year- old girls is \(54.5\) inches. Suppose a random sample of 1510 -year-old girls from Brazil is taken and that these girls had a sample mean height of \(53.2\) inches with a standard deviation of \(2.5\) inches. Assume that heights are Normally distributed. (Source: cdc.gov) a. Determine whether the population mean for height for 10 -year-old girls from Brazil is significantly different from the U.S. population mean. Use a significance level of \(0.05\). b. Now suppose the sample consists of 40 girls instead of \(15 .\) Repeat the test. c. Explain why the \(t\) -values and \(\mathrm{p}\) -value for parts a and \(\mathrm{b}\) are different.

Independent or Paired State whether each situation has independent or paired (dependent) samples. a. A researcher wants to compare food prices at two grocery stores. She purchases 20 items at Store A and finds the mean and the standard deviation for the cost of the items. She then purchases 20 items at Store \(\mathrm{B}\) and again finds the mean and the standard deviation for the cost of the items. b. A student wants to compare textbook prices at two bookstores. She has a list of textbooks and finds the price of the text at each of the two bookstores.

Tomatoes The weights of four randomly and independently selected bags of tomatoes labeled 5 pounds were found to be \(5.1\), \(5.0,5.3\), and \(5.1\) pounds. Assume Normality. a. Find a \(95 \%\) confidence interval for the mean weight of all bags of tomatoes. b. Does the interval capture \(5.0\) pounds? Is there enough evidence to reject a mean weight of \(5.0\) pounds?

Ages A study of all the students at a small college showed a mean age of \(20.7\) and a standard deviation of \(2.5\) years. Are these numbers statistics or parameters? Explain. b. Label both numbers with their appropriate symbol (such as \(\bar{x}, \mu, s\), or \(\sigma)\).

Babies Weights (Example 2) Some sources report that the weights of full-term newborn babies have a mean of 7 pounds and a standard deviation of \(0.6\) pound and are Normally distributed. a. What is the probability that one newborn baby will have a weight within \(0.6\) pound of the mean - that is, between \(6.4\) and \(7.6\) pounds, or within one standard deviation of the mean? b. What is the probability the average of four babies' weights will be within \(0.6\) pound of the mean - that is, between \(6.4\) and \(7.6\) pounds? c. Explain the difference between a and b.

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