Seminar 3 Flashcards
What assumptions need to be met in order for independent samples t-tests to work propeperly?
1.The IV is a factor with two levels (e.g., male vs female)
2.The DV is a numerical variable
3.The DV is fairly normal
4.The variance of the DV between the two levels is similar
Which of the assumptions from the conditions of a t-test are parametric assumptions
- The DV is fairly normal
- The variance of the DV between the two levels is similar (in other words the two groups have equal spread of data)
What is the difference between a one-tailed and a two-tailed test?
One tailed is directional (i.e., you expect that one measurement is greater or lesser than the other). Two tailed is non-directional.
Is a one-tailed test more, or less conservative than a two-tailed test? Why is that?
Less conservative. The t critical threshold to cross the boundary of significance is smaller.
Which requires less participants and increases statistical power: Paired sample or two sample design?
Paired sample is more statistically powerful and requires less participants.
If you use Cohen’s d and found d = 0.3, How large is the effect of the IV on the DV?
Small effect(up to 0.5), however it is still a significant effect.
t(258) = 2.59, p < 0.05
What is the t-value, what are the degrees of freedom, what is the p-value?
T-value = 2.59
Degrees of freedom = 258
P-value is less than 0.05
Maria wants to make her test more conservative and changes the significance threshold from 0.05 to 0.01. Her p-value was actually 0.02. Did she still find evidence to support her hypothesis given her new significance threshold?
No. Now that she made her test more conservative, she can no longer reject the null, since the p-value is 0.02
Maria used Cohen’s d and found d = 0.3. How large is the effect of the IV on the DV?
Small effect (up to 0.5). If Maria uses a threshold of 0.05, then she found a small but significant effect of the system on satisfaction (satisfaction ~ system)
