Researchers conducted a study to investigate the relationship between caffeine consumption and alertness levels. They recruited 30 participants and assessed their alertness after consuming a caffeine-rich energy drink. The alertness ratings were recorded on a scale from 1 (very drowsy) to 10 (very alert). The sample statistics for the caffeine group mean is 7.8, the standard is 1.2 and size sample is 30. What sample size is needed if we want a margin of error within 0.5, with a 90% confidence (Use the standard deviation from the original sample to estimate )