The critical flicker frequency (cff) is the highest frequency (in cycles/sec) at which a person can detect the flicker in a flickering light source. At frequencies above the cff, the light source appears to be continuous even though it is actually flickering. An investigation carried out to see whether true average cff depends on iris color yielded the following data (based on the article "The Effects of Iris Color on Critical Flicker Frequency," J. of General Psych., 1973: 91–95): Iris colour
Brown Green Blue
26.8 26.4 25.7
27.9 24.2 27.2
23.7 28.0 29.9
25 26.9 28.5
26.3 29.1 29.4
24.8 28.3
25.7
24.5
Ji 8 5 6
Xi 204.7 134.6 169.0
xi 25.59 26.92 28.17
n=18 x=508.3
a. State and test the relevant hypotheses at significance level .05
b. Investigate differences between

Ascientist studied a population of workers to determine whether verbal praise and/or tangible rewards affect employee productivity. in the study, some workers were offered verbal praise, some were offered tangible rewards (gift cards, presents, and some were offered neither. the productivity of each participant was measured throughout the study by recording the number of daily tasks completed by each employee. which inference might the scientists make based on the given information? a.) the number of daily tasks completed by each employee may influence the dependent variable, which is whether the employee receives verbal praise, tangible rewards, or neither. b.) verbal praise and/or tangible rewards may influence the independent variable, which is the number of daily tasks completed by each employee. c.) verbal praise and/or tangible rewards may influence the dependent variable, which is the number of daily tasks completed by each employee. d.) the dependent variables, which are verbal praise and tangible rewards, may influence the number of daily tasks completed by each employee.

How many quarts of a 50% solution of acid must be added to 20 quarts of a 20% solution of acid in order to get a 40% solution of acid?

More than 450450 students traveled to a state park for a field trip. the school allowed 66 students to travel by car, and the rest traveled on 1111 buses, each of which held the same number of students. if there were ss students in each bus, which inequality best represents this situation?