Cowles and Davis (1987) collected data on the personality traits of individuals who volunteered (and didn't volunteer) for psychological research. The researchers used Eysenck's personality inventory to measure each participant's neuroticism and extraversion score (on a scale of 0-24, with higher scores indicating more neurotic/ extraverted). You can assume this data represents a random sample from the population of interest and that the observations are independent.

What would be the appropriate test to determine if average neuroticism score differs based on volunteer status? Could you explain? thanks