In a repeated-measures experiment, each individual participates in one treatment condition and then moves on to a second treatment condition. one of the major concerns in this type of study is that participation in the first treatment may influence the participant's score in the second treatment. this problem is referred to as
1) individual differences.
2) practice effects.
3) homogeneity of variance.
4) bi-treatment effect.

2.2°  

step-by-step explanation:

let θ = the angle of elevation.

tanθ =77/2020

tanθ = 0.038 12

      θ = tan⁻¹0.038 12

      θ = 2.2°

m∠a is 90°

m∠b is 40°

the revenue of the fitness center, y, is the product of two factors: the number of members and the fee paid by each member. there are 320 members now, but number of members goes down by 10 for each $5 increase in fees, so if x is the number of $5 price increases then members is equal to (320 - 10x). since the fee is currently $45, and the fee increases by $5 for every price bump x, the fee is given by (45 + 5x). so, revenue y is given by y = (320 - 10x)(45 + 5x).