Chapter Eleven: Understanding Statistics in Research

What are the five possible results you may find as a result of your statistical analysis?

1. significant results that agree with those predicted by the researcher. 2. nonsignificant results 3. significant and unpredicted results (results are the opposite of those that were predicted by the researcher) 4. mixed results 5. unexpected or serendipitous results

What does regression analysis do?

Regression analysis can be used to predict the value of one variable when the value of one or more other variables is already known. Example: can we predict the length of a hospital stay of a patient with a certain diagnosis?

What is effect size?

The degree to which the phenomenon is present in the population, or the degree to which the null hypothesis is false.

Identify four types of descriptive statistics.

There are four types of descriptive statistics: frequency distributions (gender, ethnicity, marital status data) measures of central tendency (mean, median, mode - age data) measures of dispersion ( range, variance, standard deviation, confidence intervals, standardized scores, and scatterplots)

What statistics can be used to determine causality?

chi-square, t-tests, ANOVAs, and ANCOVAs

What are inferential statistics?

Inferential statistics are designed to address objectives, questions, and hypotheses in studies to allow inference from the study sample to the target population. They help us to: identify relationships examine predictions determine differences among groups

What is the alpha, or "level of statistical significance" for most nursing studies and what does that mean?

The alpha, or level of statistical significance for most nursing studies is 0.05. This is the probability level at which the results of the statistical analysis are judged to indicate a statistically significant difference between the groups. If the p value is less than or equal to 0.05, then the result is considered to be statistically significant. Decision theory requires that this cutoff point be absolute.

How does a researcher determine what (inferential) statistical test to use? (Yikes!!!)

There's no easy answer to this one. Usually it's a combination of the following: the study's purpose the use of questions, objectives, or hypotheses the study's design (use of groups??) the level of measurement of the variables (nominal, ordinal, interval, etc)

What are chi square and analysis of variance (ANOVA) tests used for?

To identify differences among groups in a research study.

What is probability theory?

It is used to explain the extent of a relationship, the probability that an event will occur in a given situation, , or the probability that an event can be accurately predicted.

What are limitations of a study?

Limitations are problems or restrictions in a study that may decrease the generalizability of the findings.

What is a power analysis?

Power is the probability that a statistical test will detect a significant difference that exists. A power analysis can assist you to identify the sample size you will need to avoid a Type II error (or to ensure that a significant difference exists). The minimum acceptable power level is .80

What is generalization?

the application of information that has been acquired from a specific instance to a general situation. Generalization extends the implications of the findings from the sample studied to a larger population.

What are some characteristics of significance in studies / significant studies?

the findings make an important difference in people's lives you can generalize the results far beyond the study's population / it affects large numbers of people it generates more research it contributes to theory development / becomes a theory it has implications for other disciplines besides nursing it is frequently referred to in the literature

What are the possible results that you could have with a Pearson's product-moment correlation?

A negative (inverse) relationship (the result will be close to -1) A positive relationship (the result will be close to +1) No relationship. (the result will be close to 0)

A correlational design investigates relationships between or among variables in a single population. What is the inferential statistical test most commonly used with this design?

A pearson product-moment correlation {sometimes this is just called a pearson's r or just an (r2)}. The results range from -1 to +1.

What is clinical importance?

Clinical importance is the practical relevance of the findings. There is no common agreement about how to evaluate the clinical importance of a finding.

What is decision theory?

Decision theory assumes that all of the groups in a study used to test a particular hypothesis are components of the same population relative to the variables under study. This expectation is expressed as a null hypothesis in which there is no difference between the groups.

What are descriptive statistics?

Descriptive statistics are summary statistics that allow the researcher to organize data in ways that give meaning and facilitate insight. They are calculated to describe the sample (ie. demographic statistics) and key study variables.

What does factor analysis do?

Factor analysis examines interrelationships among a large number of variables and disentangles those relationships to identify clusters of variables that are most closely linked. It can aid in the identification of theoretical concepts or be useful in the development of a new questionnaire.

What is a Type I Error?

A Type I error occurs when the null hypothesis is rejected when it is true. In plain terms...this means, that the researchers conclude that significant results exist in a study, when really, they don't.

What is a Type II Error?

A Type II error occurs when the null hypothesis is accepted when it is false. In plain terms...this means the researchers conclude that the study results are non-significant when in reality...the results were significant!

What is the purpose of conducting a confirmatory analysis?

A confirmatory analysis is used to confirm expectations regarding data from objectives, questions, or hypotheses. Inferential statistics are used, and investigators can generalize the study findings to the appropriate accessible and target population.

What is the purpose of conducting an exploratory analysis?

An exploratory analysis is used to examine all of the data descriptively.

What are statistical techniques?

Analysis procedures that are used to examine, reduce, and give meaning to the numerical data gathered in a study. For our class, there are two major categories for statistics: descriptive statistics and inferential statistics.

When a researcher uses a survey or questionnaire, how do they know it is reliable? Hint: What statistic is used, and what is considered to be a "good number"?

Reliability of a survey or a questionnaire is tested using a statistical test called a Cronbach's alpha. A Cronbach alpha value greater than .80 means that the questionnaire is considered to be reliable. Note: Researchers will report Cronbach alpha values for PAST use of the survey or questionnaire (in other studies) and in the CURRENT study.

How does a researcher describe a sample?

Variables relevant to the sample are called demographic variables (age, gender, educational levels). Demographic variables are usually described with descriptive statistics.