As part of a study on the bluntnose minnow ( Pimephales notatus ) you want to de
ID: 3317562 • Letter: A
Question
As part of a study on the bluntnose minnow (Pimephales notatus) you want to determine which factors contribute to how many of these fish live in parts of a stream. So you sampled 80 different sections of a stream and counted the number of minnows per cubic meter, the water temperature (°C), the water depth (meters), and whether or not there was a predator present (yes/no). After confirming all relevant assumptions, you ran a general linear model predicting the density of bluntnose minnows:
b
SE
Intercept
-4.61
0.45
Water Temp
0.51
0.37
Water Depth
12.33
5.13
Predator (0=No, 1=Yes)
-8.71
1.56
A)Calculate the test statistics for each explanatory variable in the model. Which predictors explain a significant amount of variation in the response variable?
B) Write out the full regression equation for predicting the density of bluntnose minnows in this stream.
C) Interpret the estimate (slope) for Predator in context.
D) Predict the bluntnose minnow density in a part of the stream that is 12°C, 2.5 meters deep, and has a predator present.
b
SE
Intercept
-4.61
0.45
Water Temp
0.51
0.37
Water Depth
12.33
5.13
Predator (0=No, 1=Yes)
-8.71
1.56
Explanation / Answer
A) Formula T = b/SE
T critical value = 1.99
Decision rule : if T statistic < -1.99 or > 1.99, then the variable is significant
b) Multiple regression equation
Density of bluntnose minnows = 0.51*water temp + 12.33*water depth - 8.71*predetor
c) if predetor increases 1 unit, then density of bluntnose minnows will be decreased by 8.71 units
d) prediction of density of bluntnose minnows
= 0.51*12 + 12.33*2.5 - 8.71*1
= 28.235
predictor b SE T decision water temp 0.51 0.37 1.378 not significant water depth 12.33 5.13 2.404 significant predetor -8.71 1.53 -5.693 significantRelated Questions
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