If the estimated population standard deviation based on previous studies is 20 percent, the acceptable error is plus or minus 5 percent, and the z-value for a 95 percent level of confidence is 1.96, the needed sample size is approximately:
A) 48.
B) 210.
C) 61.
D) 153.
E) 196.

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The Answer of If the estimated population standard deviation based on previous studies is 20 percent, the acceptable error is plus or minus 5 percent, and the z-value for a 95 percent level of confidence is 1.96, the needed sample size is approximately:
A) 48.
B) 210.
C) 61.
D) 153.
E) 196.

If the Estimated Population Standard Deviation Based on Previous Studies