Group Statistics
Fertilizer
N
Mean
Std. Deviation Std. Error Mean
Growth One
12
14.25
Two
12
13.08
4.181
4.660
1.207
1.345
Growth Equal variances assumed
Equal variances not
assumed
Levene's Test for Equality of
Variances
Independent Samples Test
Sig
F
Sig.
t
df
One-Sided
032
860
646
22
.26
646
21.745
26
Independent Samples Effect Sizes
Standardizer Point Estimate
Growth Cohen's d
Hedges' correction
Glass's delta
4.427
4.585
4.660
95% Confidence Interval
Lower Upper
.264
-.543
1.064
254
-.525
1.028
250
-.562
1.052
a. The denominator used in estimating the effect sizes.
Cohen's d uses the pooled standard deviation.
Hedges' correction uses the pooled standard deviation, plus a correction factor.
Glass's delta uses the sample standard deviation of the control (i.e., the second)
group.
It's spring and gardening season is upon us!
The manufacturer of fertilizer 1 is trying to make the claim that his product is significantly
better than fertilizer 2 when it comes to plant growth. He conducted a between subjects
experiment using his company's fertilizer (1) and his competitior's fertilizer (2) to demonstrate that
his product leads to significantly higher plant growth. (See results of SPSS output above)
A) Based on the results of this experiment, is he able to make the claim that his company's
product (Fertilizer 1) leads to significantly higher plant growth than his competitor's
product (Fertilizer 2)?
B) The manufacturer of Fertilizer 1 is planning to replicate the experiment. Considering
you're all newly-minted statisticians capable of giving advice on research design, what
recommendations do you have for him based on the outcome of the first experiment?
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(Utilize the concept of means, effect sizes, and p-values in your response)