A researcher computes the pooled variance for two samples and obtains a value of 120. If one of the samples has n = 5 scores and the second has n = 10 scores, then what is the value of the estimated standard error for the sample mean difference? Explain your response.
-the square root of (120/15)
-the square root of (120/13)
-the square root of (120/5 + 120/10)
-the square root of (120/4 + 120/9)