Chapter 7-Sampling: Estimating the Frequency of Behaviors & Beliefs Flashcards
What is the difference between a sample and a population?
A sample is a part of a population, the group that is selected to represent the population. To better understand, think about when you go to the grocery store and they give you a sample of a bag. The bite you take in the moment is a sample of the population which is the box or bag that sample came from. You don’t need to eat the whole box or bag to know whether you like it or not, you only need to test a small sample.
Understand the importance of both randomization and reducing bias in selecting a sample.
o A sample is biased when it is unrepresentative of the population because it would cause the researchers to draw the draw the wrong conclusions about the study.
♣ For example: when you are at the grocery store sampling a bag of pita chips, and you happened to get the one burnt pita chip from the whole bag, the sample would be biased because it is not representative of the quality of the bag.
♣ Another example: students on ratemyprofessor.com, this sample could be biased because the students who rate professors are usually those who are angry or disgruntled, meaning that they might not represent the rest of the professor’s students very well.
If the relationship between two variables changes depending on the level of a third variable in association research, what is this third variable called?
moderator
Which of the following is a categorical variable?
base played by baseball player, they are numbered by they have categories
Mischel (1972) studied delay of gratification in preschoolers: Children were offered a special reward if they could wait or a less attractive treat if they chose not to wait. A follow-up study was done years later, looking at the same children as adolescents. Associations were found between the waiting times of the preschoolers and behaviors of the same children as adolescents. Parents rated various self-control skills on a Likert-type scale and also completed a personality test for their adolescents. Overall, a positive relation between waiting time as a preschooler and self-control in adolescence emerged. Why isn’t this a causal relationship?
interna validity was not established, there was no manipulated variable so there may have been other alternative explanations for the results.
Kevin is studying the relationship between obesity and depression. He develops classifications for obesity based on body weight. His classmate, Hugo, suggests that this classification is flawed. What part of construct validity is Hugo challenging?
face validity —the Construct Validity means : How Well Was Each Variable Measured?—Hugo is questioning whether what is being measured by body weight is obesity.
Professor Fofana offers extra credit points in his introductory psychology classes. He wonders which students take advantage of this. He makes a scatterplot for his classes, with the number of extra credit points earned on the x-axis and the numerical grade in course without extra credit on the y-axis. He finds that r = 0.179. What does this correlation tell him about which students take advantage of the extra credit option?
Students with higher numerical grades are more likely than students with lower numerical grades to do extra credit work. the relationship is positive, meaning the slope is upward.
Professor Fofana offers extra credit points in his introductory psychology classes. He wonders which students take advantage of this. He makes a scatterplot for his classes, with the number of extra credit points earned on the x-axis and the numerical grade in course without extra credit on the y-axis. He finds that r = 0.179. According to Cohen’s conventions, how strong is this association?
small, or weak, because an r of about 0.10 is a small or weak effect size.
Vida is studying the connection between school grades and time spent using social media. She finds a strong correlation, showing the students with lower grades spend more time using social media. She decides that before she can claim that increased use of social media causes grades to drop she must check the students’ grade history. What criterion of causality is she concerned with?
temporal precedence– To make a causal claim, she needs to establish that the increased social media use preceded the low grades.
Which type of validity is typically not relevant to association claims?
Internal validity —is typically not relevant to association claims because both variables are being measured, and neither is being manipulated.
Mischel (1972) studied delay of gratification in preschoolers: Children were offered a special reward if they could wait or a less attractive treat if they chose not to wait. A follow-up study was done years later, looking at the same children as adolescents. Associations were found between the waiting times of the preschoolers and behaviors of the same children as adolescents. Parents rated their adolescents for various self-control skills on a Likert-type scale. What type of analysis should be used to look at two variables at a time?
bivariate correlation–Although the study looked at several aspects of self-control, an analysis of bivariate correlations looks at two variables at a time.
To look at the relationship between reaction time and proficiency in tennis, experts and non-experts are compared. What statistic could be used to describe the relationship?
point-biserial correlation —Reaction time is a quantitative variable and expert/non-expert is a categorical variable so the point-biserial correlation can be used to describe the relationship.
Which of these is not required to establish causality?
convergent validity— concurrent validity is used to measure construct validity.
Professor Fofana offers extra credit points in his introductory psychology classes. He wonders which students take advantage of this. He makes a scatterplot for his classes, with the number of extra credit points earned on the x-axis and the numerical grade in course without extra credit on the y-axis. He decides the plot will be clearer if he converts the numerical grades into letter grades and plots a histogram with letter grades on the x-axis and the percentage of students in each letter grade earning extra credit on the y-axis. What type of statistic would he use to describe this relationship?
point biserial correlation— Letter grades are a categorical variable so this is an analysis of one categorical variable and one quantitative variable. A point-biserial correlation is a statistic used to describe this type of relationship.
The Flynn effect, the widespread increase in intelligence scores over the last century, is unexplained. One proposed explanation is that the lowest performers have improved because of better nutrition and more widespread availability of education, and this improvement in the lowest performers has been what has raised the averages for the population. To explore this explanation, what statistical validity question should be considered?
are there subgroups?— This explanation suggests that the lower scoring performers form a subgroup and the correlation for this group should be computed separately and compared to that of the rest of the performers.
