2.3 Sample collection and selection
Thirty one hundred and ninety eight faecal specimens were collected from
sporadic cases of acute gastroenteritis in patients < 5 years
of age. These patients were admitted to four sites, namely Pune
(Maharashtra state, n = 1007), Mumbai (Maharashtra state, n = 654),
Ahmadabad (Gujarat state, n = 441), and Surat (Gujarat state, n = 1096)
during the period of 2013-16. The data on RVA testing and genotyping
analysis has been published earlier (Girish Kumar et al. 2020).
From a 3198 faecal specimens stored at -70°C, it was decided to test
representative samples for HAdV. Assuming a 50 ±/- 5% prevalence rate
of the unknown agents, the required sample size for each region was
calculated to be 384. However, due to cost constraints, only 300 samples
were selected at random by the Simple Random Sampling method from each
region (Pune, Mumbai, Surat, and Ahmadabad). To confirm that the random
sample from each region was properly representative of all samples
available from that region, the expected frequencies for each parameter
(age group, gender, year/month of the collection, vesikari score, and
Rotavirus A (RVA) positivity) in the random sample were calculated by
using corresponding percentages in the entire data. Then the observed
frequencies in the random sample were compared with expected frequencies
by using the chi-square test. The p-value >0.05 for each
comparison showed that the random sample was properly representative of
the entire set of samples in each region.