Question

Is narcissism – roughly translated as an excessive focus on oneself – a more common personality trait today than it was a few decades ago?  It is known that the mean population score on the Narcissistic Personality Inventory (NPI) for students attending University of South Alabama around 20 years ago was μ= 15 (Twenge, 2010).  Interested in the narcissism levels of students in the year 2020, a researcher administers the NPI to a random sample of 25 University of Alabama sophomores this Spring term. The mean NPI score from the researcher’s sample of sophomores is M = 16.5, with s = 3.4.

(a).

Calculate the standard error.

Type your calculations if possible. Example:   (100 - 90) /(sqrt(25))  =  10/5 = 2

Answer 1

a. Let us assume that population is normally distributed so Standard error is