reezing). The estimated regression function was

=0.1838 + 0.0272x+ 0.0446x²

with

R²= 0.860.

(a)Suppose that

n=60.

Does the quadratic model appear to be useful? Test the appropriate hypotheses. Use a significance level of 0.05.Calculate the test statistic. (Round your answer to two decimal places.)

F= 175.07

Use technology to calculate theP-value. (Round your answer to four decimal places.)

P-value = 0.00

b) Using sb2 = 0.0103, carry out a test at significance level 0.01 to decide whether the quadratic predictor x2 is important. Calculate the test statistic. (Round your answer to two decimal places.)

The standard deviation of the statistic

= a + b₁(45) + b₂(2,025)

is

s = 0.120.

Calculate a confidence interval with confidence level 90% for mean MDH activity when conductivity is 45. (Round your answers to three decimal places.)