Hypothesis Testing Part-1: Introduction and One-Sample Z-Test

[@1234nobu]

Sir, In this video at 17:10 minutes you have asked a question to reconsider the decision to reject or accept Ho if the confidence is 99%. For 99% confidence the Zcritical is 2.325. Since Zcalculated = 2.83 is still towards the right of the Zcritical, we need o to reject the null hypothesis Ho and accept alternate hypothesis H1.

[@instituteofqualityandrelia7902]

Yes Ambarish! You are right!

[@bhushan797]

One of the best teacher for DOE .. hats of to you

[@instituteofqualityandrelia7902]

Thank you! I'm glad to know that you liked it!

[@anilbp]

Splendid explanation and task too.

[@instituteofqualityandrelia7902]

Thank you Anil!

[@RajanKaushikPharmacy]

Best ever teacher and explanation ❤️

[@1234nobu]

Hemant sir, In this video, you have asked us to solve a practice problem at 17.25 minutes. I tried to solve this problem as below. Ho: The mean construction time is < 10 weeks with the new organization structure. H1: The mean construction time is >= 10 weeks with the new organization structure. The population means is 10 weeks. The standard deviation is 1.5 weeks The sample mean(from the given data) is 9.8 weeks. Zcalculated will be = (9.8-10)/(1.5*sqrt(10)) = -0.04216 With a confidence level of 95% and we need to look at the left tail of the standard normal distribution curve at 0.475 value. (0.95/2 = 0.475) The Zcritical = -0.065 Since Zcalculated (-0.04216) is towards the left of Zcritcal(-0.065), we can accept the Null Hypothesis i.e. The mean construction is

[@instituteofqualityandrelia7902]

Hello Ambarish! Thanks for your efforts. My apologies for late response! The calculation Zcalculated will be = (9.8-10)/(1.5*sqrt(10)) = -0.04216 has an error. 1.5*sqrt(10) should be 1.5/sqrt(10). This is the standard error of mean and for a sample size of n=10, it will be sigma/sqrt(n) that is 1.5/sqrt(10). With this, Zcalculated is -0.42. Also the alternate hypothesis should be H1: The mean construction time is not equal to 10 weeks with the new organization structure. This is because the problem mentions "Has mean time CHANGED"! If the statement was "Has the mean time INCREASED", then your alternate hypothesis would be correct. The Z-critical on the left tail is also incorrect. It should be -1.96 as alpha risk of 5% is distributed equally on both the tails. The conclusion, however, does not change! Hope this helps! My best wishes for DIwali!