Implementing Measurements and Testing Models Essay

Implementing Measurements and Testing Models - Essay Example Sampling is done primarily because a population may be very large and diverse making it impossible for the researchers to study all of them given the available resources as well as the element of time. The Sloven formula is commonly used to compute for the desired sample size based on the total population and the margin of error or confidence level. The formula for computing the sample size is as follows: To determine the sample population for a study on drug use of prisoners in the State facilities, the researcher may use stratified random sampling. Stratified random sample involves subdividing the population into smaller homogenous groups to get more accurate information (Best, 2003). It is a commonly used probability method that is superior to random sampling because it reduces sampling error. A stratum is a subset of the population that shares at least one common characteristic. Examples of stratums might be males and females, or managers and non-managers. The researcher first identifies the relevant stratums and their actual representation in the population. Random sampling is then used to select a sufficient number of subjects from each stratum. "Sufficient" refers to a sample size large enough for us to be reasonably confident that the stratum represents the population. Stratified sampling is often used when one or more of the stratums in the population have a low incidence re lative to the other stratums (http://www.statpac.com/surveys/sampling.htm) Since prisoners are detailed in several areas spread all throughout Oklahoma, distributing the sample population according to the area or location of the facility and relative to the number of inmates in each area would ensure representation of each facility. Assuming that the survey research will be conducted in the facilities under the Oklahoma State Department of Corrections, and the desired margin of error is 1% or at 99% confidence level, we can compute for the desired sample size of a population such as 20,306 inmates as of December 8 figures in the OkDOC database using Sloven formula - n = N/(1+Ne2) n = 20,306 / 1+ [(20,306 ) (.01) 2 ] n = 20,306 / 1 + [ (20,306) (.0001)] n = 20,306 / 1 + 2.0306 n = 20, 306 / 3.306 n = 6,142.16 or 6143 Thus, the total number of respondents to the survey on drug use among inmates in the Oklahoma State Department of Corrections will be 6,142 inmates. This figure will be drawn proportionally from the different facilities throughout the State according to their actual count of inmates. Based on percentage share computed in Appendix A, the following will be the distribution of inmate-respondent in each facility. Table 1 - Distribution of Respondents per Facility FACILITIES NAME % of total pop'n # of respondent per facility** 1. Charles E. "Bill" Johnson Correctional Center 2.1 129 2. Dick Conner Correctional Center 4.7 289 3. Dr. Eddie Warrior Correctional Center 3.7 227 4. Howard McLeod Correctional Center 3.1 190 5. Jackie Brannon Correctional Center 3.6 221 6. James Crabtree Correctional Center 3.9 240 7. Jess Dunn Correctional Center 4.8 295 8. Jim E. Hamilton Correctional Center 3.4 209 9. John Lilley Correctional Center 3.6 221 10. Joseph Harp Correctional Center 6.8 418 11. Lexington A & R Center 2 123 12. Mabel Bassett Correctional Cent