Chamberlain - Mathematics: Statistics

Chamberlain - Mathematics: Statistics Verification A sample where the population is divided into groups, several groups are randomly selected, and all from those selected groups are sampled. Data at the nominal level can be put in a category. Data at the interval level can be put in a category, put in order, and you can find differences between values. Therefore, more types of calculations can be performed with data at the interval level than with data at the nominal level. The four levels of measurement, in order from lowest to highest, are nominal, ordinal, interval, and ratio. Data at the nominal level of measurement are qualitative only. Data at this level are categorized using names, labels, or qualities. No mathematical computations can be made at this level. Data at the ordinal level of measurement are qualitative or quantitative. Data at this level can be arranged in order, or ranked, but differences between data entries are not meaningful. Data at the interval level of measurement are quantitative only. Data at this level can be ordered and differences between data entries are meaningful, but a zero entry is not an inherent zero. Data at the ratio level of measurement are quantitative only. Data at this level are similar to data at the interval level, with the added property that a zero entry is an inherent zero. A frequency distribution can sometimes be described by one of the following terms. Symmetric If a vertical line is drawn through the middle of the graph, the resulting halves are approximately mirror images. Uniform All classes in the distribution have equal frequencies. A uniform distribution is also symmetric. Skewed left The tail of the graph of the distribution elongates more to the left. Skewed right The tail of the graph of the distribution elongates more to the right. Blinding A technique where the subjects do not know whether they are receiving a treatment or a placebo. In a double-blind experiment, neither the experimenter nor the subjects know if the subjects are receiving a treatment or a placebo. Since the subjects do not know which treatment they receive already, blinding the researcher would create a double-blind experiment. Histogram Vertical bar chart that shows frequency on the y-axis. Population Collection of all counts that are of interest Qualitative Data Consists of attributes, labels, or nonnumerical entries Sample A subset or part of a population Stratified sample A sample where the population is divided into groups, and several are randomly sampled from each group.