uji q ketepatan ketelitian
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1.Uji Q
2.Ketepatan dan Ketelitian
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(1) Measurement data:0.189, 0.169, 0.187, 0.183, 0.186, 0.182, 0.181, 0.184, 0.181, 0.177
Q Test
Do the smallestand largestpoints need to be discarded?
ble
Number of values:
3 4 5 6 7 8 9 10
Q90%: 0.941 0.765 0.642 0.560 0.507 0.468 0.437 0.412
Q95%: 0.970 0.829 0.710 0.625 0.568 0.526 0.493 0.466
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Q Test
In statistics, the Qtestis used for identification and rejection of
outliers.
To apply a Qtest for bad data, arrange the data in order of increasing
values and calculate Qas defined:
Q(calculated)= Qgap/Qrange
Where Qgap =|outlier - value closest to the outlier|Qrange=|highest valuelowest value |
If Qcalculated> Qtable, DISCARD the questionable point.
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(1) For the data:
0.189, 0.169, 0.187, 0.183, 0.186, 0.182, 0.181, 0.184, 0.181, 0.177
Arranged in increasing order:
0.169, 0.177, 0.181, 0.181, 0.182, 0.183, 0.184, 0.186, 0.187, 0.189
Outlier is 0.169. Calculate Q:
With 10 observations at 90% confidence, Qcalculated< Qtable. Thereforekeep 0.169 at 90% confidence.
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The following replicate observations were
obtained during a measurement and theyare arranged in ascending order:
6.69, 6.18, 6.28, 4.85, 6.49
Can we reject observation 4.85 as an outlier
at a 95% confidence level?
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The following masses, in grams, were recorded in an
experiment to determine the average mass of a U.S.
penny:
3.067, 3.049, 3.039, 2.514, 3.048, 3.079, 3.094, 3.109,
3.102
Determine if the value of 2.514 g is an outlier at 95%
confidence level.
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1). Rata-rata (mean) dan standar deviasi (deviation)
2). Ketepatan (accuracy) dan ketelitian (precision)
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Rata-rata (mean)
The mean, X, is the numerical average obtained by dividing the sum
of the individual measurementsby the number of measurements
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Table Berat Uang Koin
What is the mean for the data in Table above?
Answer:
3.080 + 3.094 + 3.107 + 3.056 + 3.112 + 3.174 + 3.198 = 21.821
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Standard Deviation)
The absolute standard deviation, s, describes the spread of
individual measurements about the mean
Relative Standard Deviation X 100%
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What are the standard deviation, the relative standard
deviation, and the percent relative standard deviation for the
data in Table above ?
Table Berat Uang Koin
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Hasil pengukuran berat
koin bisa dituliskan sbb:
Berat koin = 3.1170.051g
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Accurate and Precise
Conceptual illustration
Accuracy and Precision
Accurate, but not Precise
Precise, but not accurate Not accurate, Not Precise
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ACCURACY
Accuracy can be defined as how close a
number is to what it should be.
Accuracy is determined by comparing anumber to a known or accepted value.
Assessing Accuracy
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Assessing Precision
Measurement of precision for a data set is the standard deviation (s)
For data sets that have more than 20 points
For data sets < 20 points
Relative Standard Deviation X 100%
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Example 1:
How old are you?
I am 22 years old (1)
I am 22 years and 8 months old (2)
I am 22 years, 8 months, and 5 days old
(3)
I am 22 years, 8 months, 5 days, and 10
hours old (4)
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Accuracy vs. Precision for
Example 1 Statement (2) is more accurate and more
precise that statement (1).
Statement (3) is more accurate and moreprecise than statement (2).
Statement (4) is more accurate and more
precise than statement (3).
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Example 2:
How long is a string ?
Student A measures the string at 2.63
0.02 m.
Using the same ruler, Student B
measures the string at 1.980.01 m.
Who is most precise?
Who is most accurate?
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Accuracy vs. Precision for
Example 2 The actual measurement is 2.65 m.
Student A is fairly accurate and also very
precise.
Student B is very precise, however, he is
not very accurate. The lack of accuracy is
due to using the ruler incorrectly.
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Accuracy vs. Precision for
Example 3 The actual measurement is 3.01 g.
Student A is reasonably accurate. He/She
was not very precise because the balancewas not capable of measuring to twodecimal places.
Student B is much more accurate because ofthe precision of his/her measurement andcloseness of her value to the actual value.
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