Bagian ini membahas salah satu distribusi peluang kontinu terpenting dalam statistika, yaitu distribusi normal.

1. DISTRIBUSI PELUANG KONTINU
• Distribusi Normal
• Distribusi Gamma
• Distribusi Eksponensial
• Distribusi Weilbull
• Distribusi t
• Distribusi F
• Distribusi Chi-square

2. DISTRIBUSI NORMAL
• Distribusi peluang kontinu terpenting dalam
statistika
• Kurva berbentuk bel
• Aplikatif dalam pengukuran fisik
• Nama lain: distribusi Gauss

3. 36.0 36.2 34.8 36.0 34.6 38.4 35.4 36.8
34.7 33.4 37.4 38.2 31.5 37.7 36.9 34.0
34.4 35.7 37.9 39.3 34.0 36.9 35.1 37.0
33.2 36.1 35.2 35.6 33.0 36.8 33.5 35.0
35.1 35.2 34.4 36.7 36.0 36.0 35.7 35.7
38.3 33.6 39.8 37.0 37.2 34.8 35.7 38.9
37.2 39.3

6. CIRI KURVA NORMAL
• Letak modus di x = µ.
• Kurva simetris terhadap sumbu vertikal yang melalui rata-rata
µ.
• Kurva bertitik belok di x = µ ± σ, cekung ke bawah untuk µ - σ
< X < µ + σ dan cekung ke atas pada bagian lainnya.
• Sumbu horizontal merupakan garis asimtot yang dihampiri
kurva menuju kedua arah yang menjauh dari rata-rata.
• Luas daerah di bawah kurva dan di atas sumbu vertikal adalah
1.

8. VARIANCE OF THE NORMAL DISTRIBUTION
• MEASURES THE SPREAD OF THE CURVE
Variance < Variance < Variance
Standard < Standard < Standard
Deviation Deviation Deviation
• MEASURE DISTANCE FROM THE MEAN () IN UNITS OF THE STANDARD
DEVIATION

9. DISTRIBUSI NORMAL BAKU
(STANDARD NORMAL DISTR.)
Distribusi normal dengan ciri-ciri:
• Rata-rata = 0
• Simpangan baku = 1

11. CONTOH PENERAPAN DISTRIBUSI
NORMAL (1)
• A certain type of storage battery lasts on the average 3.0
years, with a standard deviation of 0.5 year. Assuming that
the battery lives are normally distributed, find the
probability that a given battery will last less than 2.3 years.
• An electrical firm manufacturers light bulbs that have a
length of life that is normally distributed with mean equal
to 800 hours and a standard deviation of 40 hours. Find the
probability that a bulb burns between 778 and 834 hours.

12. CONTOH PENERAPAN DISTRIBUSI
NORMAL (2)
• In an industrial process the diameter of a ball bearing
is an important component part. The buyer sets
specification on the diameter to be 3.0 ± 0.01 cm.
The implication is that no part falling outside these
specifications will be accepted. It is known that in the
process the diameter of a ball bearing has a normal
distribution with mean 3.0 and standard deviation
0.005. On the average, how many manufactured ball
bearings will be scrapped?

13. CONTOH PENERAPAN DISTRIBUSI
NORMAL (3)
• A certain machine makes electrical resistors
having a mean resistance of 40 ohms and a
standard deviation of 2 ohms. Assuming that
the resistance follows a normal distribution
and can be measured to any degree of
accuracy, what percentage of resistors will
have a resistance that exceeds 43 ohms?