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Descriptions of three studies are given. In each of the studies, the two populations of interest are students majoring in science at a particular university and students majoring in liberal arts at this university. For each of these studies, indicate whether the samples are independently selected or paired. Study 1: To determine if there is evidence that the mean number of hours spent studying per week differs for the two populations, a random sample of 100 science majors and a random sample of 75 liberal arts majors are selected. Study 2: To determine if the mean amount of money spent on textbooks differs for the two populations, a random sample of science majors is selected. Each student in this sample is asked how many units he or she is enrolled in for the current semester. For each of these science majors, a liberal arts major who is taking the same number of units is identified and included in the sample of liberal arts majors. Study 3: To determine if the mean amount of time spent using the campus library differs for the two populations, a random sample of science majors is selected. A separate random sample of the same size is selected from the population of liberal arts majors.

Short Answer

Expert verified
Study 1 and Study 3 use independently selected samples, while Study 2 uses paired samples.

Step by step solution

01

Identify sampling for Study 1

In Study 1, a random sample of science majors and a random sample of liberal arts majors are independently chosen, without any specified connection or pairing between individuals in the two groups. Hence, this implies that the samples are independently selected.
02

Identify sampling for Study 2

In Study 2, a random sample of science majors is selected. Moreover, each science major is paired with a liberal arts major who is enrolled in the same number of units. This process establishes a direct relationship between each individual in the two groups, therefore, it implies that the samples are paired.
03

Identify sampling for Study 3

In Study 3, random samples of science majors and liberal arts majors are chosen, but no connection is made between individuals in the two groups. Consequently, the samples are independently selected.

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Key Concepts

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

Independent Samples
When conducting studies or experiments, independent samples are those in which the selection of participants from one group does not influence or relate to the selection of participants from another group. This is common in comparative research where two distinct populations are being studied.
  • For example, in Study 1 and Study 3 from the original exercise, separate groups of science and liberal arts majors were randomly selected without any pairing or interaction between them.
  • Each group is analyzed independently to investigate differences, ensuring the results relate solely to the studied variables.
  • Benefits of using independent samples include simplicity in study design and analysis, as well as reduced potential biases due to lack of pairing.
The key idea is that each sample influences its own results only, maintaining the integrity and independence of the outcomes. Analyzing independent samples typically involves statistical methods like the independent t-test or ANOVA, which compare mean values between groups.
Paired Samples
Unlike independent samples, paired samples have a methodical connection or pairing between individuals in the two groups being studied. This method is particularly useful when researchers want to control for certain variables that might otherwise introduce variability.
  • In Study 2 from the original exercise, each science major was paired with a liberal arts major taking the same number of units, creating a direct correlation between the two groups.
  • This pairing allows researchers to control external factors, like course load, thus isolating the variable of interest, such as spending on textbooks.
  • Paired samples require different statistical approaches, such as the paired t-test, to analyze differences, as these tests anticipate some natural covariance between paired observations.
Pairing reduces variability caused by extraneous factors, making it easier to observe the true effect of the independent variable. It's crucial when the aim is to closely monitor change or effect in comparative settings.
University Student Populations
University student populations often provide an excellent backdrop for conducting various statistical analyses due to their diverse demographic and academic characteristics. When selecting these populations for studies, researchers look to understand behavioral, financial, and academic differences or similarities.
  • Studies like the ones mentioned often compare students by their majors to explore trends such as study habits, spending, and library usage.
  • Researchers need to consider the diversity within this population, like age, socioeconomic background, and course difficulty, which can all affect the variables being measured.
  • Utilizing university populations can lead to impactful insights that influence policy and educational strategies.
Proper sampling and study design are crucial to deriving meaningful, generalizable results from these populations. By accurately defining and measuring variables within this context, researchers can provide valuable contributions to educational research and practice.
Comparative Study Analysis
Comparative study analysis focuses on identifying and explaining differences or similarities between groups, often involving two or more distinct populations. This method is essential in scientific research to draw meaningful conclusions about the factors being studied.
  • Studies 1 to 3 each exemplify comparative study analysis by looking at two groups within a university setting: science majors and liberal arts majors.
  • The primary aim is to assess whether there are significant differences in variables such as study hours, spending on textbooks, and library usage.
  • Results from such studies can guide strategic decision-making and policy development, contributing to improved educational outcomes.
Comparative analysis often uses inferential statistics to determine if observed differences are statistically significant. It enables researchers to understand complex relationships between variables and to differentiate between causation and correlation. Ultimately, it helps in formulating hypotheses that can be tested and validated in future research endeavors.

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Most popular questions from this chapter

The article "Plugged In, but Tuned Out" (USA Today, January 20,2010 ) summarizes data from two surveys of kids ages 8 to 18 . One survey was conducted in 1999 and the other was conducted in \(2009 .\) Data on the number of hours per day spent using electronic media, consistent with summary quantities given in the article, are given in the following table (the actual sample sizes for the two surveys were much larger). For purposes of this exercise, assume that the two samples are representative of kids ages 8 to 18 in each of the 2 years the surveys were conducted. Construct and interpret a \(98 \%\) confidence interval estimate of the difference between the mean number of hours per day spent using electronic media in 2009 and \(1999 .\) $$ \begin{array}{llllllllllllllll} 2009 & 5 & 9 & 5 & 8 & 7 & 6 & 7 & 9 & 7 & 9 & 6 & 9 & 10 & 9 & 8 \\ 1999 & 4 & 5 & 7 & 7 & 5 & 7 & 5 & 6 & 5 & 6 & 7 & 8 & 5 & 6 & 6 \end{array} $$

Babies born extremely prematurely run the risk of various neurological problems and tend to have lower IQ and verbal ability scores than babies who are not premature. The article "Premature Babies May Recover Intelligence, Study Says" (San Luis Obispo Tribune, February 12,2003 ) summarized medical research that suggests that the deficit observed at an early age may decrease as children age. Children who were born prematurely were given a test of verbal ability at age 3 and again at age 8 . The test is scaled so that a score of 100 would be average for normal-birth-weight children. Data that are consistent with summary quantities given in the paper for 50 children who were born prematurely were used to generate the accompanying Minitab output, where Age 3 represents the verbal ability score at age 3 and Age8 represents the verbal ability score at age \(8 .\) Use the information in the Minitab output to construct and interpret a \(95 \%\) confidence interval for the change in mean verbal ability score from age 3 to age 8 . You can assume that it is reasonable to regard the sample of 50 children as a random sample from the population of all children born prematurely. Paired T-Test and Cl: Age8, Age3 Paired \(\mathrm{T}\) for Age8 - Age3 \(\begin{array}{lrrrr} & \mathrm{N} & \text { Mean } & \text { StDev } & \text { Se Mean } \\ \text { Age8 } & 50 & 97.21 & 16.97 & 2.40 \\ \text { Age3 } & 50 & 87.30 & 13.84 & 1.96 \\ \text { Difference } & 50 & 9.91 & 22.11 & 3.13\end{array}\)

Babies born extremely prematurely run the risk of various neurological problems and tend to have lower IQ and verbal ability scores than babies that are not premature. The article "Premature Babies May Recover Intelligence, Study Says" (San Luis Obispo Tribune, February 12,2003 ) summarized medical research that suggests that the deficits observed at an early age may decrease as children age. Children who were born prematurely were given a test of verbal ability at age 3 and again at age 8 . The test is scaled so that a score of 100 would be average for normal-birth-weight children. Data for 50 children who were born prematurely were used to generate the accompanying Minitab output, where Age 3 represents the verbal ability score at age 3 and Age8 represents the verbal ability score at age \(8 .\) Use the Minitab output to determine if there is convincing evidence that the mean verbal ability score for children born prematurely increases between age 3 and age 8 . You can assume that it is reasonable to regard the sample of 50 children as a random sample from the population of all children born prematurely. $$ \begin{aligned} &\text { Paired T-Test and Cl: Age8, Age3 }\\\ &\begin{array}{l} \text { Paired } T \text { for } \text { Age8 - Age3 } \\ \begin{array}{rrrrr} & \text { N } & \text { Mean } & \text { StDev } & \text { Se Mean } \\ \text { Age8 } & 50 & 97.21 & 16.97 & 2.40 \\ \text { Age3 } & 50 & 87.30 & 13.84 & 1.96 \\ \text { Difference } & 50 & 9.91 & 22.11 & 3.13 \\ \text { T-Test of mean difference } & =0(\mathrm{vs}>0): \text { T-Value }=3.17 \\ \text { P-Value }=0.001 & & & \end{array} \end{array} \end{aligned} $$

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 \(\alpha=0.05\).

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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