Astronomy MC: En la lista de las 25 estrellas del diagrama HR A. la mayora de las estrellas son estrellas de tipo m ya que esas son las ms comunes B. Las estrellas de tipo B estn sobrerrepresentadas C. las estrellas ms luminosas de la galaxia estn sobrerrepresentadas D. todas las estrellas son estrellas de secuencia principal.

1. (a)Suppose for PolyU students, the average price of smartphones they pay is $4500 with a
standard deviation of $2400. If a random sample of 45 students is selected from PolyU, what is the
probability that the mean price of their smartphones is less than $4200?
(b) A random sample of 8 notebook computers with the N1 processor is selected and the prices (in
HK$) of these computers are listed below:
7500 9700 14490 8999 6299 12499 13290 8799
i. Construct a 95% confidence interval for the mean price of all notebook computers with the N1
processor. State any assumption(s)/approximation(s) used and inter- pret your result.
ii. Determine the sample size required if we want to be 95% confident that the error of our estimate
is at most HK$750. State any assumption(s)/ approximation(s) used.
(c) In a random sample of 200 staff from PolyU, it is found that 126 of them have adopted work
from home in 2021. Construct a 99% confidence interval for the true proportion of PolyU staff who
have adopted work from home in 2021.