2. Identifying populations, samples, statistics, parameters, and variables A psy

Question

2. Identifying populations, samples, statistics, parameters, and variables A psychology professor wants to know whether study skills are related to memory quality in current first-year students at her small college. Participants in the study (first-year students at her college) complete an online memory task. The students are first shown a list of 60 words. Next they are shown a list that includes 10 words that were on the original list. Then they are asked to identify the words on the second list that appeared on the original list. She uses the percentage of words that were correctly recognized on the original list as her measure of memory quality. She also asks the students to report several characteristics such as their age, their gender, and a self-assessment of their study skills. Each of the 1,000 first-year students (543 males and 457 females) at her school volunteers to participate. The professor chose 100 students at random to complete the memory task and answer the questions. The average percentage of words that were correctly recognized on the original list was 68%. The professor infers that if all 1,000 first-year students had completed the study, the results would show that an average of 68% (plus or minus sampling error) of the words were correctly recognized as being on the original list. Which of the following are variables in the study? Check all that apply The students, percentage of words that were correctly recognized on the original list The students' self-assessments of their study skills The 100 students The 1,000 students

Explanation / Answer

1. Variables in the study are:

Conceptual information:

Variables are the attributes that are under consideration for inference. Thus in this particular study, the students % of words that were correctly recognized and the students self assessment of their study skills are both variables.

2. Population in the study is :

The 1,000 first-year students at the college.

Conceptual information:

Now the population refers to the entire cohort of people for whom we need to infer results for, in this case the 1000 first year students at college.

3. Sample in the study is :

The 100 students who participated in the study.

Conceptual information:

Now it is not possible to study the entire population due to time and cost factors, and hence we select and analyse the sample from the population to infer results about the attribute under considerion. In this case the sample being that of the 100 students who participated in the study.

4. A Statistic in the study is:

68%, the average percentage of words that were correctly recognized as being from the original list by the 100 students.

Conceptual information:

A statistic is a measure of some attribute of a sample and in this case, the the average percentage of words that were correctly recognized as being from the original list by the 100 students.

5. A parameter in the study is :

The actual average percentage of words that would be correctly recognized as being from the original list by the 1,000 first year students.

Conceptual information:

Parameters are numbers that are used in summarizing data for an entire population and thus in this case study it would be the actual average percentage of words that would be correctly recognized as being from the original list by the 1,000 first year students.

5. An example of the professor using descriptive statistics:

She characterizes the first year students at the college as consisting of 543 males and 457 females.

Conceptual information:

Descriptive statistics is used to describe what the data shows.

6. An example of the professor using inferential statistics:

She infers that if all 1,000 students had done the experiment, the results would show that an average of 68%(plus or minus sampling error) of the words were correctly recognized as being on the original list.

Conceptual information:

With inferential statistics, we try to reach conclusions based on the sample data i.e. conclusions about the population that extend beyond the provided sample data.

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