Suppose that a researcher, using data on class size (CS)(CS)and average test scores from 103 third-grade classes, estimates the OLS regression

\widehat {Testscore}=556.828-6.2274CS, \text{ R}^2=.09, \text{SER}=12.3.

(a) A classroom has 20 students. The regression's prediction for that classroom's average test score is__ . (Round your response to two decimal places.)

(b) Last year a classroom had 17 students, and this year it has 21 students. The regression's prediction for the change in the classroom average test score is__ . (Round your response to two decimal places.)

(c) The sample average class size across the 103 classrooms is 22.90.The sample average of the test scores across the 103 classrooms is ___. (Hint: Review the formulas for the OLS estimators.) (Round your response to two decimal places.)

(d) The total sum of squares is ___ . (Hint: Review the formulas for the \text{R}^2R2 and \text{SER}.SER.) (Round your response to the nearest whole number.)

answer: 60

step-by-step explanation:

1/2a + (2/3×30)   = 50

1/2a + 20 = 50

1/2a = 30

a = 60

the answer   is 200

step-by-step explanation:

this is a problem about poisson probabilities.   i don't know if you've

already studied poisson distributions, or if you have a place to look

to read more about the subject.  

here's how you can see a poisson distribution coming.   when there are

a lot of events that may happen at any time (or any place), and when

you're counting how many of them happen at a particular time (or a

particular place), and each event is independent of the others, then

the result is a poisson distribution.   this is roughly true for the

chocolate chips; one chip being in a cookie has only a small effect on

the probability that another chip will be in the cookie.

once you know you have a poisson distribution, you know a lot.   there

is only one parameter to a poisson distribution, so if you know the

mean, you know everything.   the form of the distribution is

  probability of n chips = {[e^(-x)]*(x^n)} / (n! )

25/6

step-by-step explanation:

you multiply 4 by the denominator (4*6=24) and add it to the numerator which makes it 25/6.