Should I use a 5- or 7-point Likert scale?

Though traditional Likert scales include a 5-point response scale, some research has indicated that 7-point scales provide more reliable results.

As a rule of thumb, 5-point scales are better for unipolar constructs, which range from zero to positive, such as frequency. You may want to use 7-point scales for bipolar (or dichotomous) constructs that range from negative to positive, such as quality—some evidence suggests that doing so can increase reliability.