Li designed a survey to determine how comfortable students at her middle school are with fractions. there are 600 students in her middle school. the students are equally distributed among grade levels. she selected a sample of 28 students in her first-period class. which best explains li’s sample?
a. random and biased
b. random and unbiased
c. nonrandom and biased
d. nonrandom and unbiased

Any is very appreciated! (picture is provided below)not sure how to do this at all won't lie

In the diagram of circle o, what is the measure of zabc?

Agroup of student volunteers participates in a study designed to assess several behavioral interventions for improving output in a repetitive task. prior to the beginning of the study, all volunteers unknowingly observed, and their output is measured. at the beginning of the study, prior to any intervention, the volunteers perform the same task under the observation of a study administrator, and their overall output increases. which of the following terms describes this phenomenon? a. simpson's paradox b. hawthorne effect are d. novelty effect d. pygmalion effect e. observer-expectancy effect