A certain manufacturer produces computer chips; each chip is independently acceptable with some unknown probabilityp. To obtain an approximate 99 per- cent confidence interval for p, whose length is approximately .05, an initial sample of 30 chips has been taken. If 26 of these chips are of acceptable quality, then the preliminary estimate ofpis 26/30. Using this value, a 99 percent confidence interval of length approximately .05 would require an approximate sample of size.