Question

Part 1) In order to calculate the variance, which of the following must you know?

1. Range
2. Median
3. Mean
4. Mode

Why?

Part 2) How could we measure how many pieces of candy each kid takes?

Part 3) I suggest you use Lee Becker’s pooled variance program. Let’s say you have a study looking at the DV “Time to help”. Your IV is whether potential helpers did not see (condition #1) or saw (condition #2) someone else helping. The mean time to help for those in condition #1 was 58 seconds (variance was 2.81). The mean time to help those in condition #2 was 55 seconds (variance was 3.06). First, tell me what Cohen’s d (pooled) is. Second, tell me if the effect size is meaningful in terms or magnitude!

Answer 1

## Part 1) In order to calculate the variance, which of the following must you know?

1. Range
2. Median
3. Mean
4. Mode

Why?

Answer : 3 ) mean  

we know that variance formula or definition ,

The variance is defined as the sum of the squared distance of each term in the distribution from the mean

divided by the number of terms in the distribution , you can take the sum of the squares of the terms in the

distribution , and divide by the number of terms in the distribution .

## Part 2) How could we measure how many pieces of candy each kid takes?

Answer : we can use here sample mean , it is preferred to use measure in this example .

## Part 3) I suggest you use Lee Becker’s pooled variance program. Let’s say you have a study looking at the DV “Time to help”. Your IV is whether potential helpers did not see (condition #1) or saw (condition #2) someone else helping. The mean time to help for those in condition #1 was 58 seconds (variance was 2.81). The mean time to help those in condition #2 was 55 seconds (variance was 3.06). First, tell me what Cohen’s d (pooled) is. Second, tell me if the effect size is meaningful in terms or magnitude!

Answer :

we have given two samples :

sample 1 = condition 1 and

sample 2 = condition 2

for sample 1 : M1 = 58 and S1 ^2 = 2.81 and

for sample 2 = M2 = 55 and  S2 ^2 = 3.06

we have to find Cohen's d : effect size

Cohen's d = ( M1 - M2 ) / SD pooled )

where SD pooled = √ ( S1 ^2 + S2 ^2) /2 =  √ ( 2.81 + 3.06) / 2 = 1.7131

Cohen's d = ( M1 - M2 ) / SD pooled ) = ( 58 - 55 ) / 1.7131

= 3 / 1.7131

= 1.7151

( it is large effect )

If Cohen's d is bigger than 1 , the difference between the two means is larger than one standard deviation