Learn how to estimate 95% confidence intervals for Cronbach's alpha (a.k.a., coefficient alpha) in SPSS. Actually, the procedure can calculate any confidence intervals you specify (e.g., 90%, 95%, 99%). The procedure is accomplished by estimating a two-way mixed model intraclass correlation coefficient, as that statistic is identical to Cronbach's alpha. Here are the two references I mention in the video:

Baumgartner, T. A., & Chung, H. (2001). Confidence limits for intraclass reliability coefficients. Measurement in Physical Education and Exercise Science, 5(3), 179-188.

Bravo, G., & Potvin, L. (1991). Estimating the reliability of continuous measures with Cronbach's alpha or the intraclass correlation coefficient: toward the integration of two traditions. Journal of clinical epidemiology, 44(4-5), 381-390.