Question

1. Lucy always uses an alpha level of 0.01 (two-tailed). Charlie always uses an alpha level of 0.05 (two-tailed). Which researcher is more likely to make a Type I Error. Lucy or charlie?

2. A researcher is interested in whether blood pressure decreases among adults who eat dark chocolate. The mean systolic blood pressure of the population is 135 with a standard deviation of 15. She tests a sample of 100 adults who eat dark chocolate and finds their mean systolic blood pressure to be 120. What is the null hypothesis?

   		μ = 135
   		μ ≠ 135
   		μ  > 135
   		μ ≥ 135

3. According to Cohen's d conventions, which of the following would be considered to be a medium effect size?

   		-0.55
   		0.81
   		-0.98
   		0.17

4. With α = 0.05, what is the critical t value for a one-tailed test with n = 15?

   		t = 1.761
   		t = 1.753
   		t = 2.145
   		t = 2.131

5. What z-score values form the boundaries for the middle 68% of a normal distribution?

   		z = +0.2 and z = - 0.2
   		z = +0.4 and z = - 0.4
   		z = +0.8 and z = - 0.8
   		z = +1.0 and z = - 1.0

Answer 1

Solution:

Question 1)

Lucy always uses an alpha level of 0.01 (two-tailed).

Charlie always uses an alpha level of 0.05 (two-tailed).

Level of significance is nothing but P( Type I Error)

So as alpha level increases, P( Type I Error) increases.

thus

Charlie researcher is more likely to make a Type I Error.

Question 2)

The mean systolic blood pressure of the population is 135 with a standard deviation of 15.

that is:

A researcher is interested in whether blood pressure decreases among adults who eat dark chocolate.

thus this is left tailed test, thus H1 is < type

then null hypothesis H0 would be ≥ type.

Thus correct answer is:

μ ≥ 135

Question 3)

A Cohen's d value close to 0.5 is considered as medium effect.

Thus from given options: -0.55 , we use absolute value = 0.55 close to 0.5

hence 0.55 has medium effect

thus correct answer is:

-0.55

Question 4)

With α = 0.05, what is the critical t value for a one-tailed test with n = 15?

df = n - 1 = 15 - 1 = 14

One tail area = 0.05

t = 1.761

Question 5)

What z-score values form the boundaries for the middle 68% of a normal distribution?

According to Empirical rule:

68% of the data falls within 1 standard deviation from mean

thus z values are: -1.00 and 1.00

thus correct answer is:

z = +1.0 and z = - 1.0