CHAPTER 16 STUDY GUIDE

Chapter 16: Descriptive Statistics
Definition- Statistics used to describe the basic features of the study population. Main concepts include: Frequency Distributions, Central Tendency, Variability, and Risk Indexes.
Levels of Measurement
Nominal- assigning numbers to classify categories. For example, 1 for blood type A and 2 for Blood type B
Ordinal- classification based on ranking. For example, 1 –Poor, 2-Good, 3-Excellent
Interval- Interval scales that assume similarity in the difference between values. For example, 20-40 degrees and 50-70 degrees.
Ratio- Measurements that give rank on an attribute, exact interval, and meaningful attribute. For example height.
FREQUENCY DISTRIBUTIONS -Arrangement of values (x) from lowest to highest and the number of times each value is attained (f).
A set of data is described using 3 characteristics;
Shape of Distributions- Displayed in Graphs using histograms and polygons whose shapes describe data as either skewed, positively skewed, or negatively skewed.
Central Tendency- Use a single value to represent a data set.
Statistical methods used;
Mode- Most frequent occurring value. Used to quickly determine a popular score.
Median- Value at the midpoint. Preferred for a skewed distribution.
Mean- Average value. Majorly used in interval and ratio measurements
Variability- How dispersed or spread distribution is.
Statistical methods used;
Range- Highest value minus lowest value. Mainly used as an unrefined descriptive index.
Standard Deviation-The amount of deviation of a value from the mean score.

A more stable and refined index of variability.
Other statistical methods (Bivariate-two variables)
Crosstables-Two-dimensional distributions with two variables cross-tabulated. Used in nominal and ordinal measurements with few ranks.
Correlation- Relationship between two variables. Used with two variables in either ordinal, interval or ratio measurements.
RISK INDEXES
Used to describe data to enable clinical decision making.
Absolute Risk- Proportion of people both exposed and not exposed to a risk factor.
Absolute Risk Reduction- Proportion of people who may be spared the risk factor through intervention.
Relative Risk- Proportion of original risk of a risk factor.
Relative Risk Reduction-Proportion of untreated risk reduced through intervention.
Odds Ratio-Proportion of people with the adverse outcome to those without
The number needed to treat- Number of people needed to receive intervention to prevent one undesired outcome.
In the nursing field, understanding descriptive statistics is crucial since it can be used to understand and carry out research studies as well as make the right clinical decisions. They are used to draw insights into a study sample. Statistical methods under this category have been used in research studies, for example, the average mortality rate in the United States, and the relationship between lifestyle patterns and increasing the risk of diabetes. However, critiquing descriptive statistics they are not appropriate for a population study and nurses in their research should consider whether the information is adequate, and appropriate statistical methods were used.

References
Polit, D. F., Beck, C. T., & Polit, D. F. (2017). Resource manual for Nursing research, generating and assessing evidence for nursing practice, tenth edition. Philadelphia, PA: Wolters Kluwer.