Question

SpaceX decided to send 10 male rats into space. Upon their return, the red blood cell mass

(in millilitres) o f the rats was determined. A control group o f 10 male rats was held under thesame conditions (except for space flight) as the space rats, and their red blood cell mass was also determined when the space rats returned. SpaceX wants to determine i f there is a difference in red blood cell mass between the two groups after space flight. An Excel output of the comparison of the groups at the 1% level of significance is below.

t-Test: Two-Sample Assuming Equal Variances Flight Control Mean Variance Observations Pooled Variance 0.948833 Hypothesized Mean df t Stat P(T<-t) one-tai0.398264 t Critical one-tail P(T<=t) two-tail | 0.796528 8.158 0.930738 0.966929 10 8.044 10 0 18 -0.26169 2.55238 ritical two-tai 2.87844

a) State the null and alternate hypotheses.

b) At the 1% level does the evidence suggest that the space rats have a different red blood cell mass from the control group? Use the above Excel output to justify.

c) What type of en-or could be committed during this test (aside from sending rats to space)?

Answer 1

(a) Ho: μ1 = μ2 and Ha: μ1 ≠ μ2

(b) The two-tail p- value is 0.796, which is > 0.01. So, we can't reject Ho. This means we do not have sufficient evidence that the two groups have significantly different means.

(c) In this test, we failed to reject Ho. If we had rejected Ho, we would be making a type I error.

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