The population is the collection of response variable measurements on all

experimental units in the universe. The collection of observations of IGF-1 receptors on

each gingival tissue sample make up the population. The U-sample is the collection of

experimental units included in the study and the P-sample is the collection of response

variable measurements from the U-sample. In this report the U-Sample is the collection

of gingival tissue samples in this study and the P-Sample is the expression of IGF-1

receptors on the human gingival tissue samples collected.

 This is an observational study as it contains only observational factors. The

response variable is ordinal as it can be ranked subjectively (grade I, II, or III). Ordinal

response variables are the only type of response variable which do not have common

distributions to determine mathematically. Hence, they are referred to as distribution

free. The statistical analysis of ordinal response variables has historically not involved

parameters. This has led to the development of a group on analyses generally referred to

as nonparametric because they are not based on population parameters. Thereby

validating the use of analysis for linear trend and proportions.