Two separate samples are being used to estimate the population mean difference between two treatment conditions. Which of the following would produce the widest confidence interval?

1.
n1 = n2 = 10 with a pooled variance of 100
2.
n1 = n2 = 10 with a pooled variance of 10
3.
n1 = n2 = 20 with a pooled variance of 100
4.
n1 = n2 = 20 with a pooled variance of 10