Question 1

Outliers are best detected by examining the

Accepted Answer

Frequency distribution produces a list of how often a value appears, which makes it easy to identify outliers (values outside the normal distribution range). The mean is an arithmetic average of a value set and SD is the average amount each value in a distribution varies from the mean.

Question 2

A one-tailed test of significance should be used if the research hypothesis is

Accepted Answer

A one-tailed test of significance is associated with a directional hypothesis or a statement about a certain type of difference or relationship that is expected. Positive and negative refer to the skew of a distribution of scores or the direction of a relationship.

Question 3

If a distribution of scores is characterized by very few extremely high or extremely low values, with most values clustering around the mid-range, this distribution would be described as

Accepted Answer

Clustering around mid-range is an example of a normal (or bell-shaped) distribution. A distribution is positively skewed if values cluster at the low end of the scale and the tail tapers off to the high end, indicating very few high values for the variable. A negatively skewed distribution is characterized by a predominance of high values and very few low values.

Question 4

If the distribution of values for a data set is characterized by very few high values and a preponderance of low values, it would be described as

Accepted Answer

A distribution is positively skewed if values cluster at the low end of the scale and the tail tapers off to the high end, indicating very few high values for the variable. A normal distribution is characterized by clustering around mid-range, whereas a negatively skewed distribution is characterized by a predominance of high values and very few low values.

Question 5

The distribution for the variable "number of days hospitalized in a general hospital" would most likely be

Accepted Answer

Number of days hospitalized would most likely be characterized with a cluster at the low end and very few high values or lengthy stays. Normal and negatively skewed would not characterize number of days hospitalized.

Question 6

In a skewed distribution of values, the mean will be

Accepted Answer

The mean is the combined average of the group and so it will be pulled in the direction of the skew. The middle value is the median and the modal value is the most frequently occurring, representing the prevailing view.

Question 7

A sampling distribution of means is

Accepted Answer

A sampling distribution of means is constructed from the means of an infinite number of samples of the same size that have been randomly drawn from the same population. Thus, it is always hypothetical.

Question 8

A researcher collects data on education and codes it as follows:
1 = less than high school
2 = high school completion or GED
3 = some post-high school education
4 = AA degree or completion of trade school
5 = BA or equivalent
6 = graduate education
The most appropriate measure of central tendency for these data would be the

Accepted Answer

The median is appropriate as an index of typicalness for ordinal, interval, and ratio levels of data. The mean is the appropriate measure of central tendency when what is of interest is the total or combined average performance of a group. The mode is the only measure of central tendency that can be used with nominal data.

Question 9

Which of the following statistical indices is best for describing the heterogeneity of values in a data set?

Accepted Answer

The standard deviation is an indication of the homogeneity or heterogeneity of a data set. The standard deviation can be used to interpret the location or probability of an individual value in a distribution, in that values that lie farther away from the mean (in standard deviation units) are less likely to occur. The range reflects the span of values in a data set.

Question 10

Which of the following distributions of scores is most homogeneous?

Accepted Answer

The standard deviation is an indication of the homogeneity or heterogeneity of a data set, with smaller values indicating a more homogeneous distribution. The smallest standard deviation for the examples is 5.

Question 11

Which of the following pairs of measures would indicate the most heterogeneous set of normally distributed scores?

Accepted Answer

A heterogeneous set of scores would have a larger standard deviation than a homogeneous set of scores. Mean = 100, range = 50 is incorrect because we do not have information about how scores are distributed between the high and low values of the data set.

Question 12

The mean test scores for three groups are 22.35, 25.75, and 30.35. The researcher examines these scores using ANOVA; results are F = 3.16 (2, 57), p = 0.04. Based on these results, the researcher can conclude

Accepted Answer

Because the p value in this situation is less than 0.05, the researcher can reject the null hypothesis and conclude that the difference between the groups is unlikely to be due to chance. A statistically significant F does not, however, indicate which groups are different; this requires post hoc analysis.

Question 13

A researcher wants to compare differences in hospital length of stay for preterm infants who are randomly assigned to four different methods of stimulation. Which statistical test should be used in this situation?

Accepted Answer

One-way ANOVA is used is to compare the mean value for an interval- or ratio-level variable for three or more groups. ANCOVA compares mean performance while controlling for the effects of a covariate. Factorial ANOVA examines the main and interaction effects of two or more independent variables.

Question 14

A researcher wants to compare NCLEX scores for students from ADN and BSN programs in two states. The most appropriate statistical test for this situation would be

Accepted Answer

In this situation, the researcher is simultaneously considering the effects of two independent variables (state and type of program), so factorial ANOVA is the correct response. Chi-squared examines the relationship between two nominal-level variables. An independent t-test examines mean performance for two unrelated groups.

Question 15

The relationship between gender and specialty area among nurses could be described by using which of the following procedures?

Accepted Answer

A contingency table can be used to depict the relationship between a pair of categorical (i.e., nominal or ordinal) variables. A contingency table is simply a two-way frequency distribution or cross-tabulation of two variables. Pearson's r is used to describe the relationship between two interval- or ratio-level variables and is the correlation coefficient that is reported most frequently in the research literature. In contrast, t-tests are parametric statistical procedures that are used when a researcher wants to compare the mean performance or value for a characteristic in two groups.

Question 16

A researcher wants to test the difference between average weights of a group of nursing home residents before and after a new food service program is put in place. Which statistical test should be used in this situation?

Accepted Answer

A dependent samples t-test is used when the researcher want to compare the means of two related groups or paired measures such as pre- and post- scores. Chi-squared would be used to compare the frequency of a nominal-level variable. Repeated measures ANOVA would be used to compare three or more measures of the same dependent interval- or ratio-level dependent variable.

Question 17

A researcher hypothesizes that pain intensity levels of postoperative cardiovascular surgery patients will be higher when they are walking on a treadmill than when walking in their own home. The appropriate statistical test for examining this hypothesis is

Accepted Answer

A t-test is used to compare mean performance on an interval- or ratio-level dependent variable for two groups. ANCOVA is used to compare mean performance while controlling for the effects of covariates. Factorial ANOVA is used to examine main and interaction effects of two or more independent variables.

Question 18

What does a researcher's level of significance represent?

Accepted Answer

Recall that the p value attached to a calculated statistic represents its level of significance (or alpha level) or the probability that the outcome occurred by chance. The actual p value attached to a statistic indicates the Type I error rate if the null hypothesis is rejected. The other two answers are incorrect. A Type II error is related to power, which is the probability that a statistical test will detect a difference or relationship, if one exists. The clinical significance of a difference might be indicated by the actual magnitude of the difference between measures.

Question 19

A researcher commits a Type I error when

Accepted Answer

Type I error (sometimes called the alpha error) occurs when a researcher rejects a null hypothesis that really is true. In other words, researchers commit a Type I error when they claim a difference or relationship exists when, in fact, it does not.

Question 20

Which of the following statements is true?

Accepted Answer

A 0.01 level of significance reflects a 1% chance of making a Type I error when the null hypothesis is rejected; a 0.05 level of significance reflects a 5% chance of making a Type I error. A decreased Type I error rate corresponds to an increased Type II error rate. If results are statistically nonsignificant, they cannot be rejected. However, this does not necessarily mean the null hypothesis is true because of the risk of a Type II error.

Quiz 12: Data Analysis in Quantitative Research