A small pilot study is being conducted to determine the association between maternal age and birth weight.
First, from all the single births in 2009 at Hospital X with mothers aged ? 20 years, we randomly selected 15 records. We also selected randomly 17 records from all the single births with mothers aged > 20 years. Then we classified each newborn as weighting ? 2500 grams or > 2500 grams.
The data is summarized in the table below:
|
|
Birth weight
|
|
|
Mother's age
|
? 2500 grams
|
> 2500 grams
|
Total
|
|
? 20 years
|
5
|
10
|
15
|
|
> 20 years
|
4
|
13
|
17
|
|
Total
|
9
|
23
|
32
|
a) State the relevant null and alternative hypotheses.
b) Using a type I error level of 0.05, perform the appropriate statistical test.
c) Explain your results in 2-3 sentences.
d) If we extended the study and randomly selected 230 records from all the single births in 2009 at Hospital X (the data is shown below), would the maternal age be related to the birth-weight of the infant? Conduct test of hypothesis. Interpret the results.
|
|
Birth weight
|
|
|
Mother's age
|
? 2500 grams
|
> 2500 grams
|
Total
|
|
? 20 years
|
40
|
60
|
100
|
|
> 20 years
|
34
|
96
|
130
|
|
Total
|
74
|
156
|
230
|