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In a study of the effect of college student employment on academic performance, the following summary statistics for GPA were reported for a sample of students who worked and for a sample of students who did not work (University of Central Florida Undergraduate Research Journal, Spring 2005): $$ \begin{array}{cccc} & \begin{array}{c} \text { Sample } \\ \text { Size } \end{array} & \begin{array}{c} \text { Mean } \\ \text { GPA } \end{array} & \begin{array}{c} \text { Standard } \\ \text { Deviation } \end{array} \\ \begin{array}{c} \text { Students Who Are } \\ \text { Employed } \end{array} & 184 & 3.12 & 0.485 \\ \begin{array}{c} \text { Students Who Are } \\ \text { Not Employed } \end{array} & 114 & 3.23 & 0.524 \\ & & & \end{array} $$ The samples were selected at random from working and nonworking students at the University of Central Florida. Estimate the difference in mean GPA for students at this university who are employed and students who are not employed.

Short Answer

Expert verified
The difference in the mean GPA for students who are employed and those who are not is -0.11.

Step by step solution

01

Identify the Means

From the given data, it can be seen that the Mean GPA of students who are employed (Mean1) is 3.12 and the Mean GPA of students who are not employed (Mean2) is 3.23.
02

Calculate the Difference in Means

Subtract Mean2 from Mean1 using the formula \(difference = Mean1 - Mean2\). This will give the difference in Mean GPA of the two groups.
03

Evaluate the Mean Difference

Subtract \(3.23 (Mean2)\) from \(3.12 (Mean1)\) to get the difference. The difference would be \(3.12 - 3.23 = -0.11\). Therefore, the mean GPA of employed students is 0.11 lower than that of non employed students.

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Key Concepts

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

Mean GPA Comparison
When it comes to academic achievement, Grade Point Average (GPA) is a pivotal metric used to assess student performance. Comparing mean GPAs can provide valuable insights into the academic effects of various factors, such as employment status.In the case of the study from the University of Central Florida, researchers aimed to identify any differences in the academic performances between employed and non-employed students by comparing their mean GPAs. The mean GPA is essentially the average score of a group's academic grades, which is calculated by adding all the individual GPAs and dividing by the number of students. Here, employed students had a mean GPA of 3.12, while non-employed students had a slightly higher mean GPA of 3.23.

To determine the impact of employment on academic performance, the difference between these two means was calculated, which revealed that students who were employed had, on average, a 0.11-point lower GPA than their non-employed counterparts. This negative difference suggests that employment might be associated with a slight decline in academic performance. However, it's crucial to consider other possible factors and to understand that correlation does not imply causation without further research.
Standard Deviation
Let's delve into the concept of standard deviation, an essential statistic that measures how spread out the numbers in a data set are. In a real-world scenario like evaluating student GPAs, standard deviation offers insight into the variability of students' grades within each group.Considering our study, the standard deviation for the GPA of employed students was 0.485, whereas the standard deviation for non-employed students was 0.524. These figures indicate that the GPA scores of non-employed students are slightly more spread out than that of employed students, meaning there's more variability in the GPAs of the non-employed group.

Why is this important?

It allows us the ability to understand not just the average performance of students but also the consistency of their grades. A lower standard deviation suggests that the GPAs are closer to the mean, showing a more consistent academic performance. In contrast, a higher standard deviation indicates more diverse outcomes and hence less predictability. By understanding standard deviation, educators and students alike can get a clearer picture of the overall performance landscape.
Sample Size
When analyzing statistics, the significance of a sample size cannot be overstated. The sample size refers to the number of observations or individuals included in a study. It plays a critical role in the reliability of statistical analyses and the validity of the resulting conclusions. Larger sample sizes generally provide more precise estimates of what researchers aim to measure, reducing the margin of error and increasing the confidence in the findings.In the study comparing the GPAs of employed versus non-employed students, the sample sizes were 184 and 114, respectively. The sample size impacts the weight of the evidence provided by the study outcomes. Larger samples are typically better representations of the entire population and are less susceptible to random errors or anomalies.

What does this mean for the study?

Although both sample sizes are relatively modest, the differing sizes could introduce an element of bias or affect the precision of the GPA comparison. Ideally, for robust conclusions, similar sample sizes are preferred, as they ensure a balanced comparison between groups. Nonetheless, the provided sample sizes can still offer important preliminary insights into the relationship between employment and academic performance.

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Most popular questions from this chapter

The press release titled "Keeping Score When It Counts: Graduation Rates and Academic Progress Rates" (The Institute for Diversity and Ethics in Sport, March 16,2009 ) gave the 2009 graduation rates for African American basketball players and for white basketball players at every NCAA Division I university with a basketball program. Explain why it is not necessary to use a paired- samples \(t\) test to determine if the 2009 mean graduation rate for African American basketball players differs from the 2009 mean graduation rate for white basketball players for NCAA Division I schools.

Each person in a random sample of 228 male teenagers and a random sample of 306 female teenagers was asked how many hours he or she spent online in a typical week (Ipsos, January 25,2006 ). The sample mean and standard deviation were 15.1 hours and 11.4 hours for the males and 14.1 hours and 11.8 hours for the females. a. The standard deviation for each of the samples is large, indicating a lot of variability in the responses to the question. Explain why it is not reasonable to think that the distribution of responses would be approximately normal for either the population of male teenagers or the population of female teenagers. b. Given your response to Part (a), would it be appropriate to use the two- sample \(t\) test to test the null hypothesis that there is no difference in the mean number of hours spent online in a typical week for male teenagers and female teenagers? Explain why or why not. c. If appropriate, carry out a test to determine if there is convincing evidence that the mean number of hours spent online in a typical week is greater for male teenagers than for female teenagers. Use \(\alpha=0.05\).

For each of the following hypothesis testing scenarios, indicate whether or not the appropriate hypothesis test would be for a difference in population means. If not, explain why not. Scenario 1: The authors of the paper "Adolescents and MP3 Players: Too Many Risks, Too Few Precautions" (Pediatrics [2009]: e953-e958) studied independent random samples of 764 Dutch boys and 748 Dutch girls ages 12 to \(19 .\) Of the boys, 397 reported that they almost always listen to music at a high volume setting. Of the girls, 331 reported listening to music at a high volume setting. You would like to determine if there is convincing evidence that the proportion of Dutch boys who listen to music at high volume is greater than this proportion for Dutch girls. Scenario 2: The report "Highest Paying Jobs for \(2009-10\) Bachelor's Degree Graduates" (National Association of Colleges and Employers, February 2010 ) states that the mean yearly salary offer for students graduating with accounting degrees in 2010 is \(\$ 48,722\). A random sample of 50 accounting graduates at a large university resulted in a mean offer of \(\$ 49,850\) and a standard deviation of \(\$ 3,300\). You would like to determine if there is strong support for the claim that the mean salary offer for accounting graduates of this university is higher than the 2010 national average of \(\$ 48,722\). Scenario 3: Each person in a random sample of 228 male teenagers and a random sample of 306 female teenagers was asked how many hours he or she spent online in a typical week (Ipsos, January 25,2006 ). The sample mean and standard deviation were 15.1 hours and 11.4 hours for males and 14.1 and 11.8 for females. You would like to determine if there is convincing evidence that the mean number of hours spent online in a typical week is greater for male teenagers than for female teenagers.

Do male college students spend more time studying than female college students? This was one of the questions investigated by the authors of the paper "An Ecological Momentary Assessment of the Physical Activity and Sedentary Behaviour Patterns of University Students" (Heath Education Journal \([2010]: 116-125)\). Each student in a random sample of 46 male students at a university in England and each student in a random sample of 38 female students from the same university kept a diary of how he or she spent time over a 3 -week period. For the sample of males, the mean time spent studying per day was 280.0 minutes, and the standard deviation was 160.4 minutes. For the sample of females, the mean time spent studying per day was 184.8 minutes, and the standard deviation was 166.4 minutes. Is there convincing evidence that the mean time male students at this university spend studying is greater than the mean time for female students? Test the appropriate hypotheses using \(\alpha=0.05\).

Example 13.1 looked at a study comparing students who use Facebook and students who do not use Facebook ("Facebook and Academic Performance," Computers in Human Behavior [2010]: \(1237-1245\) ). In addition to asking the students in the samples about GPA, each student was also asked how many hours he or she spent studying each day. The two samples (141 students who were Facebook users and 68 students who were not Facebook users) were independently selected from students at a large, public Midwestern university. Although the samples were not selected at random, they were selected to be representative of the two populations. For the sample of Facebook users, the mean number of hours studied per day was 1.47 hours and the standard deviation was 0.83 hours. For the sample of students who do not use Facebook, the mean was 2.76 hours and the standard deviation was 0.99 hours. Do these sample data provide convincing evidence that the mean time spent studying for Facebook users is less than the mean time spent studying for students who do not use Facebook? Use a significance level of 0.01 .

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