First, a factorial ANOVA (Heppner, Wampold, & Kivlighan, 2008) was conducted to evaluate the percentage of students passing ELA and Math assessments within all RAMP schools (2007, 2008, and 2009) compared to a stratified sample
of students attending control schools using one data point in time only (2009 percent passing rates).
ensure that the sample proportion for the stratifying characteristic is identical to the population proportion, reducing sampling error and improving the accuracy of inferences.
A stratified sample
was drawn from the publication's rankings based upon the multiple national and regional categories of the undergraduate school rankings.
If the variance of the observed characteristic within each stratum is smaller than that for the entire population, as is usually true, the reliability of the sample for a given size will be better or the efficiency for a given degree of reliability will be greater because we used a stratified sample
For example, a four-cavity machine could be producing four distinctly different populations (strata) and the choice of selecting a random or stratified sample
affects the sensitivity of detecting a shift in one or more strata.
Although there was no statistically significant difference in the indicators of fertility between linked and unlinked cases, the differential in linkage rates was considerably more pronounced in its biasing effect than the modest departures of the 1910 stratified sample
from the national public use sample of that year.
An independent research firm will select a stratified sample
of senior credit, finance and sales/marketing professionals to participate in the focus groups.
The stratified sample
includes 270 children which is not a small sample considering the resource and time expended on individually administered devices specially with very young children.
The information about daily newspapers is derived from a changed model adopted by the Newspaper Association of America that uses a stratified sample
Although it is hard to draw population conclusions from a stratified sample
of this type, two impressions struck me.
The purpose of this study was to determine if there were significant similarities or differences in problem-solving orientations and decision-making styles among a stratified sample
of rehabilitation practitioners.
We should mark the lack of any pretense to either a random or a stratified sample