In: Statistics and Probability
Do questions A-D
Feeding behavior of black bream fish. In Brain and Behavior Evolution (April 2000), Zoologists conducted a study of the feeding behavior of black bream fish. The zoologists recorded the number of aggressive strikes of two black bream fish feeding at the bottom of an aquarium in the 10-minute period following the addition of food. The next table lists the weekly number of strikes and age of the fish (in days).
Week ? ? ? ? ? ? ? ? ?
Number of Strikes ?? ?? ?? ?? ?? ?? ?? ?? ??
Age of Fish (days) ??? ??? ??? ??? ??? ??? ??? ??? ???
We want to fit a straight-line model relating number of strikes(y) to age of fish (x).
a. Find ???? , ???? ??? ???? .
b. Find the least squares estimators ?̂ 0 and ?̂ 1 and give the least squares prediction equation.
c. Give a practical interpretation of the value of ?̂ 1.
d. Find ? 2 , the estimator of the variance ? 2 of the random error term ?.
e. Use the least squares model to estimate the mean number of strikes if the age of fish is 170 days.
f. List the assumptions required for the regression analysis.
g. Is there evidence that age of fish contributes information for the prediction of number of strikes? Conduct a hypothesis test using ? = 0.1.
h. Find a 97 % Confidence interval for ?1.
X | Y | XY | X² | Y² |
120 | 85 | 10200 | 14400 | 7225 |
136 | 63 | 8568 | 18496 | 3969 |
150 | 34 | 5100 | 22500 | 1156 |
155 | 39 | 6045 | 24025 | 1521 |
162 | 58 | 9396 | 26244 | 3364 |
169 | 35 | 5915 | 28561 | 1225 |
178 | 57 | 10146 | 31684 | 3249 |
184 | 12 | 2208 | 33856 | 144 |
190 | 15 | 2850 | 36100 | 225 |
Ʃx = | Ʃy = | Ʃxy = | Ʃx² = | Ʃy² = |
1444 | 398 | 60428 | 235866 | 22078 |
a)
Sample size, n = 9
x̅ = Ʃx/n = 1444/9 = 160.444444
y̅ = Ʃy/n = 398/9 = 44.2222222
SSxx = Ʃx² - (Ʃx)²/n = 235866 - (1444)²/9 = 4184.22222
SSyy = Ʃy² - (Ʃy)²/n = 22078 - (398)²/9 = 4477.55556
SSxy = Ʃxy - (Ʃx)(Ʃy)/n = 60428 - (1444)(398)/9 = -3428.88889
b)
Slope, b1 = SSxy/SSxx = -3428.88889/4184.22222 = -0.819481
y-intercept, b0 = y̅ - b1* x̅ = 44.22222 - (-0.81948)*160.44444 = 175.70333
Regression equation :
ŷ = 175.7033 + (-0.8195) x
c)
As the value of age of fish increases by one unit than the value of Number of strikes decreases by 0.8195 units.
d)
Sum of Square error, SSE = SSyy -SSxy²/SSxx
= 4477.55556 - (-3428.88889)²/4184.22222 = 1667.64767
Estimate of variance, s² = SSE/(n-2) = 1667.64767/(9-2) = 238.2354