Question 1

What does cluster sampling refer to, in the context of increasing the external validity of a study?

Accepted Answer

Cluster sampling uses a naturally-occurring group as a study group. Using a group of coffee drinkers and a group of tea drinkers in a study is cluster sampling; this approach is often used in marketing research.

Question 2

Different research designs and strategies are used to gain specific types of information. How does correlational research work?

Accepted Answer

Correlational research does not have internal validity, so no causal relationships can be determined. Causal relationships can be inferred in some instances. Correlational research can measure the strength of dependence between two variables that is not otherwise accounted for (causally, or by their response to other variables).

Question 3

Frequency distribution provides a summary of a data set and indicates number of cases at any given score within a given range. Which of the following statements refers to skewed distribution?

Accepted Answer

Skewed distribution has asymmetrical frequency distributions. In either a positively or negatively skewed data set, values are not evenly distributed on either side of the mean.

Question 4

In statistics, standard error of the mean refers to the expected error of a given sample mean. Which of the following statements is not true about standard error of the mean?

Accepted Answer

Standard error of the mean decreases as N decreases.

Question 5

There are three main types of group design in research. Which design sometimes requires the process of counterbalancing?

Accepted Answer

Within subjects design refers to comparing groups that are related or correlated in some manner, such as from repeat measurements. Repeated measure design (one type of within subjects design) requires counterbalancing because of possible carryover effects between each measurement.

Question 6

Single-subject design in research studies one or a few subjects closely, rather than studying groups. What is one of the most common problems associated with single subject design?

Accepted Answer

Autocorrelation, which refers to the effect of measuring one individual repeatedly, is a significant problem in single-subject design. Autocorrelation is likely to produce scores that do not accurately reflect the research variables.

Question 7

Research aims to draw conclusion about relationships among variables. There are a number of threats to validity-factors that interfere with making reliable and clear conclusions. Which of the following concerns is a threat to internal validity?

Accepted Answer

Instrumentation refers to changes in researchers or calibration of equipment used in a study. This is a threat to internal validity; it is a factor other than the independent variable that might affect the dependent variable of a study.

Question 8

There are four types of data resulting from research that determine what kind of statistical test is used in analysis. What type of data involves obtaining numerical scores for each individual in a study, such as weight or age, where scores have an absolute zero?

Accepted Answer

Ratio data involve obtaining numerical scores for each individual in a study, such as weight or age. This data is then used to calculate means and make comparisons across score values.

Question 9

Descriptive statistics is used to describe the data collected from a group (the dependent variables). Group data is described using measures of central tendency. Which of those measures is the arithmetic average of a group's data?

Accepted Answer

The mean is the arithmetic average of a group's data; it is calculated by dividing the score total by total number of scores. The mean of the data set 7, 8, 23, 5, 34 is 15.4.

Question 10

In addition to being measured by central tendency, group data can be measured by variability in descriptive statistics. The standard deviation from the mean is a measure of average deviation from the mean in a set of scores. Which of the following sets of scores will have the greatest standard deviation?

Accepted Answer

The spread of scores (difference between smallest and largest number in the set) is greatest for this set, so it will have the greatest standard deviation.

Question 11

Graphs are sometimes used to represent a group's data in descriptive statistics. On a graph, the X-axis always represents categories or scores and the Y-axis always represents frequency. Interval and ratio data are depicted the same way on graphs; how are those two types of data graphed?

Accepted Answer

Interval and ratio data are both graphed with curves, rather than bar or rectangular line graphs.

Question 12

Inferential statistics procedures are used to make inferences about the general population from a study sample. Research in this field is based on a hypothesis that applies to the population and is tested using a sample. There are different types of hypotheses used in research. Which of those states that the independent variable has no effect on the dependent variable?

Accepted Answer

The null hypothesis states that the independent variable has no effect on the dependent variable. Research is conducted with the hope that differences will be found and the null hypothesis can be rejected. The alternative hypothesis states that the independent variable does have an effect on the dependent variable (that there are differences between groups).

Question 13

The central limit theorem discusses the relationship between sample size (assuming an infinite number of equally-sized samples) and mean distribution of those samples on a graph. According to the theorem the standard deviation of the means will equal what?

Accepted Answer

According to the central limit theorem, the standard deviation of the means will equal the standard deviation of the population divided by the square root of sample size.

Question 14

In an experiment designed to enhance IQ with a sample size of 25, where population mean for IQ is 100, what would be considered a statistically insignificant sample mean IQ?

Accepted Answer

A 99 is a statistically insignificant mean, because it is less than one standard error away from the population mean; the standard error of the mean in this study is 3. 110 is the most statistically significant result of these options; it is more than three standard error units away from the mean.

Question 15

In hypothesis testing, the area of the curve in which it is unlikely a researcher will obtain means is called the rejection region (or region of unlikely values). What conclusions are drawn when obtained values fall in the rejection region?

Accepted Answer

When obtained values fall in the rejection region, a researcher concludes that there are differences between groups; null hypothesis is rejected. This outcome provides statistically significant findings.

Question 16

Z-scores are a type of standard score (scores based on the standard deviation of the sample). Why is it useful to transform raw scores into z-scores?

Accepted Answer

Z-scores are useful because they correspond to percentile ranks and because they are relatively easy to calculate from raw scores. However, they only correspond to percentile ranks in normal distributions and can only be defined when population parameters are known.

Question 17

Two students take a test. Student F scores in the 92nd percentile and student K scores in the 47th percentile. If three points are added to each student's raw score, whose percentile will be more impacted?

Accepted Answer

Student K's percentile rank will be more greatly impacted by the addition of 3 points to the raw score. Percentile rank varies much more in the middle of a distribution than at either end (smaller fluctuations in raw score result in bigger fluctuations in percentile).

Question 18

A study collects information from 50 people about their ethnicity, where options are Caucasian, Hispanic, Native American, Asian, and African; and their religious views, where options are agnostic, Christian, atheist, and other. How many degrees of freedom are there?

Accepted Answer

There are 12 degrees of freedom. A multiple sample chi-square is used to analyze this data, since there are two independent variables. The formula for degrees of freedom in a multiple sample chi-square is df=(#rows-1)x(#columns-1). There are 5 rows for ethnicity and 4 rows for religious views. So, degrees of freedom is 5 minus 1 (4) times 4 minus 1 (3).

Question 19

When analyzing a one-way ANOVA, what value is used to determine significance?

Accepted Answer

F ratio is the number used to determine significance in a one-way ANOVA. F ratio is calculated by dividing the mean square between groups by the mean square within groups.

Question 20

In statistical test construction, factorial design allows for analysis of the effect of each factor on the response variable, as well as the effect of interactions between factors on the response variable. If a factorial design yields main and interaction effects, how should results be interpreted?

Accepted Answer

When analyzing results from a factorial design test, analyze the main effect while keeping in mind the interaction effect. ANOVA or regression analysis is the appropriate choice for this test.

Quiz 8: Research Stats