Nunnally, J. C. (1978). Psychometric theory (2nd ed.). New York: McGraw-Hill.

APA Citation:

Nunnally, J. C. (1978). Psychometric theory (2nd ed.). New York: McGraw-Hill.

7 point Likert scale will provide optimum reliability without creating a cumbersome number of response options. 

Nunnally, J. C. (1978). Psychometric theory, 2nd ed. New York: McGraw-Hill.

APA Citation:

Nunnally, J. C. (1978). Psychometric theory, 2nd ed. New York: McGraw-Hill.

Nunnally (1978) has suggested that score reliability of .70 or better is acceptable when

used in basic social science research.