Normal Distribution Paranormal Distribution Anna Karlin Most Slides by Alex Tsun
Agenda ● The Normal/Gaussian RV ● Closure properties of the Normal RV ● The standard normal CDF ● The Central Limit Theorem!
The Normal/Gaussian RV
The Normal PDF
<latexit sha1_base64="wqZLPcGml9Og5FDdUdFUNWEF4FE=">AB6HicbVBNS8NAEJ3Ur1q/qh69LBbBU0mqoMeiF48t2FpoQ9lsJ+3azSbsboQS+gu8eFDEqz/Jm/GbZuDtj4YeLw3w8y8IBFcG9f9dgpr6xubW8Xt0s7u3v5B+fCoreNUMWyxWMSqE1CNgktsGW4EdhKFNAoEPgTj25n/8IRK81jem0mCfkSHkoecUWOlJu2XK27VnYOsEi8nFcjR6Je/eoOYpRFKwTVu5ifEzqgxnAqelXqoxoWxMh9i1VNItZ/ND52SM6sMSBgrW9KQufp7IqOR1pMosJ0RNSO97M3E/7xuasJrP+MySQ1KtlgUpoKYmMy+JgOukBkxsYQyxe2thI2oszYbEo2BG/5VXSrlW9i2qteVmp3+RxFOETuEcPLiCOtxBA1rAOEZXuHNeXRenHfnY9FacPKZY/gD5/MHxKuM6Q=</latexit> The Standard Normal CDF 0 a
<latexit sha1_base64="wqZLPcGml9Og5FDdUdFUNWEF4FE=">AB6HicbVBNS8NAEJ3Ur1q/qh69LBbBU0mqoMeiF48t2FpoQ9lsJ+3azSbsboQS+gu8eFDEqz/Jm/GbZuDtj4YeLw3w8y8IBFcG9f9dgpr6xubW8Xt0s7u3v5B+fCoreNUMWyxWMSqE1CNgktsGW4EdhKFNAoEPgTj25n/8IRK81jem0mCfkSHkoecUWOlJu2XK27VnYOsEi8nFcjR6Je/eoOYpRFKwTVu5ifEzqgxnAqelXqoxoWxMh9i1VNItZ/ND52SM6sMSBgrW9KQufp7IqOR1pMosJ0RNSO97M3E/7xuasJrP+MySQ1KtlgUpoKYmMy+JgOukBkxsYQyxe2thI2oszYbEo2BG/5VXSrlW9i2qteVmp3+RxFOETuEcPLiCOtxBA1rAOEZXuHNeXRenHfnY9FacPKZY/gD5/MHxKuM6Q=</latexit> <latexit sha1_base64="XE2GIHEiozZRnB/MWU1YWeDNaL8=">AB8XicbVBNSwMxEJ31s9avqkcvwSLUg2W3CnosevFYwX5gu5Rsm1Ds8mSZIWy9F948aCIV/+N/+N2XYP2vpg4PHeDPzgpgzbVz321lZXVvf2CxsFbd3dvf2SweHLS0TRWiTSC5VJ8CaciZo0zDaSdWFEcBp+1gfJv57SeqNJPiwUxi6kd4KFjICDZWevTOe40Rq+CzYr9UdqvuDGiZeDkpQ45Gv/TVG0iSRFQYwrHWXc+NjZ9iZRjhdFrsJZrGmIzxkHYtFTi2k9nF0/RqVUGKJTKljBopv6eSHGk9SQKbGeEzUgvepn4n9dNTHjtp0zEiaGCzBeFCUdGoux9NGCKEsMnlmCimL0VkRFWmBgbUhaCt/jyMmnVqt5FtXZ/Wa7f5HEU4BhOoAIeXEd7qABTSAg4Ble4c3Rzovz7nzMW1ecfOYI/sD5/AF3ro95</latexit> <latexit sha1_base64="UtAQTl5HemJVA3aXQpAYqzPnUOg=">AB/nicbVDLSsNAFJ3UV62vqLhyM1iEdtGSVE3QtGNywq2FtpQbqaTdujkwcxEKHgr7hxoYhbv8Odf+MkzUJbD1w4c869zL3HjTiTyrK+jcLK6tr6RnGztLW9s7tn7h90ZBgLQtsk5KHouiApZwFtK6Y47UaCgu9y+uBOblL/4ZEKycLgXk0j6vgwCpjHCgtDcyjfmvMKjWo4its17IHVEsDs2zVrQx4mdg5KaMcrYH51R+GJPZpoAgHKXu2FSknAaEY4XRW6seSRkAmMKI9TQPwqXSbP0ZPtXKEHuh0BUonKm/JxLwpZz6ru70QY3lopeK/3m9WHmXTsKCKFY0IPOPvJhjFeI0CzxkghLFp5oAEUzviskYBClE0tDsBdPXiadRt0+qzfuzsvN6zyOIjpGJ6iCbHSBmugWtVAbEZSgZ/SK3own48V4Nz7mrQUjnzlEf2B8/gAFuJLx</latexit> <latexit sha1_base64="UyhIi9uJIiIGu7TMPZg2VlqWys=">AB8HicbVBNSwMxEJ31s9avqkcvwSLUg2W3CnosevFYwX5Iu5Rsm1Dk+ySZIWy9Fd48aCIV3+ON/+N2XYP2vpg4PHeDPzgpgzbVz321lZXVvf2CxsFbd3dvf2SweHLR0litAmiXikOgHWlDNJm4YZTjuxolgEnLaD8W3mt5+o0iySD2YSU1/goWQhI9hY6bHXGLHKOT4r9ktlt+rOgJaJl5My5Gj0S1+9QUQSQaUhHGvd9dzY+ClWhFOp8VeomMyRgPadSiQXVfjo7eIpOrTJAYaRsSYNm6u+JFAutJyKwnQKbkV70MvE/r5uY8NpPmYwTQyWZLwoTjkyEsu/RgClKDJ9Ygoli9lZERlhYmxGWQje4svLpFWrehfV2v1luX6Tx1GAYziBCnhwBXW4gwY0gYCAZ3iFN0c5L8678zFvXHymSP4A+fzBweBjz4=</latexit> The Standard Normal CDF Φ ( − a ) = 1 − Φ ( a ) Φ ( − a ) 1 − Φ ( a ) 0 a
The Standard Normal CDF
What about non-Standard Normals?
We can Standardize any RV probability students Definition of Expectation
Normals stay normal! (Under scale+Shift) probability students Definition of Expectation
Closure of the normal (Under scale+Shift) probability students Definition of Expectation
X is normal with mean 3 and variance 9. What is Pr (2 < X < 5) ○ Pr (X > 0) ○ Pr (|X-3| > 6) ○
X is normal with mean 3 and variance 9. What is Pr (2 < X < 5) ○ Pr (X > 0) ○ Pr (|X-3| > 6) ○
<latexit sha1_base64="N0Sk5aodJRL9coO8QfPWdqzEbFg=">AB+nicbVDLSsNAFJ34rPWV6tLNYBEqSEmqoMuiG1dSwT6giWUynbRDZyZhZqKU2E9x40IRt36JO/GSZuFth64cDjnXu69J4gZVdpxvq2l5ZXVtfXCRnFza3tn1y7tVSUSEyaOGKR7ARIEUYFaWqGenEkiAeMNIORleZ34gUtFI3OlxTHyOBoKGFCNtpJ5duql4PDmBnqIDju5rx8WeXaqzhRwkbg5KYMcjZ795fUjnHAiNGZIqa7rxNpPkdQUMzIpeokiMcIjNCBdQwXiRPnp9PQJPDJKH4aRNCU0nKq/J1LElRrzwHRypIdq3svE/7xuosMLP6UiTjQReLYoTBjUEcxygH0qCdZsbAjCkpbIR4ibA2aWUhuPMvL5JWreqeVmu3Z+X6ZR5HARyAQ1ABLjgHdXANGqAJMHgEz+AVvFlP1ov1bn3MWpesfGYf/IH1+QMCAZKJ</latexit> From to standard normal N ( µ, σ 2 )
Summary: The Normal/Gaussian RV
Normal random variables
Closure of the normal (under addition) probability students Definition of Expectation
Closure of the normal (under addition) probability students Definition of Expectation
5.7 The Central Limit Theorem
The Sample Mean
The Sample Mean
The Central Limit Theorem Consider i.i.d. (independent, identically distributed) random vars X 1 , X 2 , X 3 , … Where X i has μ = E[X i ] and σ 2 = Var[X i ] Consider random variables X 1 + X 2 + . . . + X n and n 1 X X i n i =1
The Central Limit Theorem Consider i.i.d. (independent, identically distributed) random vars X 1 , X 2 , X 3 , … Where X i has μ = E[X i ] and σ 2 = Var[X i ] As n → ∞, n µ, σ 2 ✓ ◆ M n = 1 X Restated: As n → ∞, X i → N n n i =1
CLT (Pictures) Fr From: https://courses.cs.washington.edu/courses/cse312/17wi/slides/10limits.pdf
CLT (Pictures) Fr From: https://courses.cs.washington.edu/courses/cse312/17wi/slides/10limits.pdf
CLT (Pictures) Fr From: https://courses.cs.washington.edu/courses/cse312/17wi/slides/10limits.pdf
CLT (Pictures) Fr From: https://courses.cs.washington.edu/courses/cse312/17wi/slides/10limits.pdf
CLT (Pictures) Fr From: https://courses.cs.washington.edu/courses/cse312/17wi/slides/10limits.pdf
CLT (Pictures) Fr From: https://courses.cs.washington.edu/courses/cse312/17wi/slides/10limits.pdf
CLT (Pictures) Fr From: https://courses.cs.washington.edu/courses/cse312/17wi/slides/10limits.pdf
CLT in the real world CLT is the reason many things appear normally distributed Many quantities = sums of (roughly) independent random vars Exam scores: sums of individual problems People’s heights: sum of many genetic & environmental factors Measurements: sums of various small instrument errors
CLT in the real world
CLT in the real world
CLT in the real world
CLT in the real world
CLT in the real world
CLT (Example) Definition of Expectation
CLT (Example) Definition of Expectation
CLT (Example) Definition of Expectation
CLT (Example) Definition of Expectation
The Continuity Correction (Idea) ● Suppose I asked you to estimate Pr (X = 20) using the normal approximation. ● Problem: Binomial is discrete, Normal is continuous.
The Continuity Correction (Idea) Definition of Expectation
The Continuity Correction (Idea) Definition of Expectation
The Continuity Correction (Idea) Definition of Expectation
The Continuity Correction
The Continuity Correction
The Central Limit Theorem
Normal random variables
The Standard Normal CDF
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