For a certain examination, a score of 58 was 2 standard deviations below the mean, and a score of 98 was 3 standard deviations above the mean. What was the mean score for the examination?
A. 74
B. 76
C. 78
D. 80
E. 82
Λύση (B):
Έστω m=mean (αριθμητικός μέσος) και d= standard deviation (τυπική απόκλιση)
m– 2d = 58
m+ 3d= 98
Αφαιρώντας τις 2 εξισώσεις μεταξύ τους βγάζουμε d= 8 .
Επομένως χρησιμοποιώντας ξανά τη πρώτη εξίσωση (είτε τη δεύτερη) m – 2*8 = 58 [katex]\Rightarrow[/katex] m= 76
![Everyone believed the team was favored with athletic talent and a seasoned, successful coaching staff; […]](https://www.uniperfect.gr/wp-content/uploads/2021/02/verbal-1.jpg)
![Although the initial cost of installing solar panels to produce electricity can be _______, the financial benefits […]](https://www.uniperfect.gr/wp-content/uploads/2021/02/math-2.jpg)