Trong cu\u1ed9c s\u1ed1ng, ch\u00fang ta th\u01b0\u1eddng c\u1ea7n ph\u1ea3i mua b\u00e1nh ng\u1ecdt, s\u1eefa b\u1ed9t, \u0111\u01b0\u1eddng, mu\u1ed1i \u0103n v\u00e0 nh\u1eefng th\u1ef1c ph\u1ea9m th\u01b0\u1eddng d\u00f9ng h\u00e0ng ng\u00e0y kh\u00e1c. Ta th\u01b0\u1eddng th\u1ea5y tr\u00ean bao b\u00ec c\u00f3 ghi tr\u1ecdng l\u01b0\u1ee3ng r\u00f2ng ghi r\u00f5 kh\u1ed1i l\u01b0\u1ee3ng v\u1eadt ph\u1ea9m. Nh\u01b0ng c\u0169ng c\u00f3 c\u00e1c bao b\u00ec ghi tr\u1ecdng l\u01b0\u1ee3ng tinh 500 \u00b1 2 g v.v\u2026 Nh\u01b0 v\u1eady c\u00f3 ngh\u0129a l\u00e0 g\u00ec? Con s\u1ed1 500 v\u00e0 2 c\u00f3 g\u00ec kh\u00e1c nhau?<\/p>\n\n\n\n
Trong cu\u1ed9c s\u1ed1ng hi\u1ec7n \u0111\u1ea1i, c\u00e1c th\u01b0\u01a1ng ph\u1ea9m th\u01b0\u1eddng \u0111\u01b0\u1ee3c \u0111\u00f3ng g\u00f3i ho\u00e0n ch\u1ec9nh b\u1eb1ng m\u00e1y \u0111\u00f3ng g\u00f3i. V\u00ed d\u1ee5 theo quy \u0111\u1ecbnh c\u00e1c t\u00fai s\u1eefa ph\u1ea3i \u0111\u01b0\u1ee3c \u0111\u00f3ng 500 g. Nh\u01b0ng do m\u00e1y \u0111\u00f3ng g\u00f3i c\u00f3 khi\u1ebfm khuy\u1ebft, do d\u00f2ng ch\u1ea3y kh\u00f4ng \u0111\u1ec1u c\u0169ng nh\u01b0 thao t\u00e1c c\u1ee7a c\u00e1c nh\u00e2n vi\u00ean \u0111\u00f3ng g\u00f3i v\u00e0 nhi\u1ec1u nguy\u00ean nh\u00e2n kh\u00e1c, tr\u1ecdng l\u01b0\u1ee3ng s\u1eefa trong t\u00fai s\u1eefa c\u00f3 th\u1ec3 c\u00f3 sai kh\u00e1c v\u1edbi quy \u0111\u1ecbnh ch\u00fat \u00edt. N\u00f3i chung tr\u00ean bao b\u00ec ghi 500 g ch\u1ec9 tr\u1ecdng l\u01b0\u1ee3ng r\u00f2ng trung b\u00ecnh, c\u00f2n \u201c\u00b1\u201d ch\u1ec9 ra r\u1eb1ng s\u1ef1 sai l\u1ec7ch c\u00f3 th\u1ec3 v\u1ec1 hai ph\u00eda d\u01b0\u01a1ng ho\u1eb7c \u00e2m, 2 gam l\u00e0 ch\u1ec9 sai s\u1ed1 trung b\u00ecnh theo ti\u00eau chu\u1ea9n c\u00f3 th\u1ec3 m\u1eafc ph\u1ea3i.<\/p>\n\n\n\n
Khi ta l\u1ea5y b\u1ea5t k\u00ec 100 t\u00fai \u0111\u1ec3 ki\u1ec3m tra th\u00ec ch\u1ea5t l\u01b0\u1ee3ng tinh m\u1ed7i t\u00fai c\u00f3 th\u1ec3 l\u00e0 X g, X l\u00e0 m\u1ed9t con s\u1ed1 kh\u00f4ng x\u00e1c \u0111\u1ecbnh c\u00f3 th\u1ec3 l\u00e0 501 g, ho\u1eb7c 498 g, ho\u1eb7c c\u00f3 th\u1ec3 l\u00e0 500 g. X \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 \u0111\u1ea1i l\u01b0\u1ee3ng thay \u0111\u1ed5i. K\u1ebft qu\u1ea3 c\u00e2n \u0111o \u0111\u01b0\u1ee3c d\u1eabn ra trong b\u1ea3ng d\u01b0\u1edbi \u0111\u00e2y:<\/p>\n\n\n\n
V\u00ec v\u1eady v\u1edbi m\u1ed9t t\u00fai s\u1eefa b\u1ea5t k\u00ec, kh\u1ea3 n\u0103ng \u0111\u1ec3 tr\u1ecdng l\u01b0\u1ee3ng r\u00f2ng c\u1ee7a s\u1eefa X = 495 g ch\u1ec9 l\u00e0 1%, X = 496 ch\u1ec9 l\u00e0 2% v.v\u2026t\u01b0\u01a1ng \u1ee9ng v\u1edbi c\u00e1c t\u1ec9 l\u1ec7 (x\u00e1c su\u1ea5t) p = 0,01. 0,02\u2026 hay ng\u01b0\u1eddi ta c\u00f3 th\u1ec3 vi\u1ebft p (X = 495) = 0,01 v.v\u2026 v\u00e0 t\u1ed5ng c\u00e1c x\u00e1c su\u1ea5t ph\u1ea3i b\u1eb1ng 1. Gi\u00e1 tr\u1ecb p \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 x\u00e1c su\u1ea5t c\u1ee7a bi\u1ebfn s\u1ed1 X \u0111\u1ec3 X l\u1ea5y m\u1ed9t gi\u00e1 tr\u1ecb n\u00e0o \u0111\u00f3 hay n\u00f3i c\u00e1ch kh\u00e1c \u0111\u00f3 l\u00e0 lu\u1eadt ph\u00e2n b\u1ed1 c\u1ee7a bi\u1ebfn s\u1ed1 X. D\u1ef1a v\u00e0o lu\u1eadt ph\u00e2n b\u1ed1 ng\u01b0\u1eddi ta c\u00f3 th\u1ec3 t\u00ednh gi\u00e1 tr\u1ecb trung b\u00ecnh a c\u1ee7a \u0111\u1ea1i l\u01b0\u1ee3ng bi\u1ebfn thi\u00ean X. a = 495 x 0,01 + 406 x 0,02 + \u2026 +504 x 0,04 + 505 x 0,01 = 500 v\u00e0 gi\u00e1 tr\u1ecb trung b\u00ecnh l\u00e0 500 g.<\/p>\n\n\n\n
Ta l\u1ea1i t\u00ednh sai s\u1ed1 c\u1ee7a \u0111\u1ea1i l\u01b0\u1ee3ng X v\u1edbi s\u1ed1 trung b\u00ecnh X – a, \u1edf \u0111\u00e2y c\u00f3 11 lo\u1ea1i sai s\u1ed1 -5, -4,\u2026 4 v\u00e0 5. Sai s\u1ed1 l\u1edbn nh\u1ea5t l\u00e0 5. Sai s\u1ed1 b\u00ecnh qu\u00e2n b s\u1ebd l\u00e0: b = |-5| x 0,01 + |-4| x 0,02 +..+ (4) x 0,04 + (5)x 0,01 =1,56<\/p>\n\n\n\n
T\u1ee9c sai s\u1ed1 trung b\u00ecnh l\u00e0 1,56.<\/p>\n\n\n\n
M\u1ed9t ph\u01b0\u01a1ng ph\u00e1p t\u00ednh sai s\u1ed1 kh\u00e1c l\u00e0 t\u00ednh ph\u01b0\u01a1ng sai \u03c32. \u03c32 = (-5)2 x 0,01 + (-4)2 x 0,03 +\u2026+42 x 0,03 +52 x 0,01 = 4 v\u00e0 \u03c3 =<\/p>\n\n\n\n
Ng\u01b0\u1eddi ta g\u1ecdi \u03c3 l\u00e0 \u0111\u1ed9 l\u1ec7ch chu\u1ea9n. Ph\u01b0\u01a1ng sai v\u00e0 \u0111\u1ed9 l\u1ec7ch chu\u1ea9n ph\u1ea3n \u00e1nh sai s\u1ed1 c\u1ee7a ph\u00e9p \u0111o.<\/p>\n\n\n\n
V\u00ec v\u1eady \u0111\u1ec3 bi\u1ec3u di\u1ec5n r\u00f5 r\u00e0ng tr\u1ecdng l\u01b0\u1ee3ng t\u1ecbnh ph\u1ea3i bi\u1ec3u di\u1ec5n 500 \u00b1 5 g v\u1edbi sai s\u1ed1 l\u1edbn nh\u1ea5t ho\u1eb7c 500 \u00b1 1,56 v\u1edbi sai s\u1ed1 tuy\u1ec7t \u0111\u1ed1i ho\u1eb7c 500 \u00b1 2 g bi\u1ec3u di\u1ec5n v\u1edbi \u0111\u1ed9 l\u1ec7ch chu\u1ea9n.<\/p>\n\n\n\n
T\u1eeb kho\u00e1: Bi\u1ebfn s\u1ed1; X\u00e1c su\u1ea5t; Lu\u1eadt ph\u00e2n b\u1ed1 sai s\u1ed1; Sai s\u1ed1 trung b\u00ecnh; \u0110\u1ed9 l\u1ec7ch chu\u1ea9n; Sai s\u1ed1 c\u1ef1c \u0111\u1ea1i.<\/p>\n\n\n\n
<\/p>\n\n\n\n\n\n\n","protected":false},"excerpt":{"rendered":"
Trong cu\u1ed9c s\u1ed1ng, ch\u00fang ta th\u01b0\u1eddng c\u1ea7n ph\u1ea3i mua b\u00e1nh ng\u1ecdt, s\u1eefa b\u1ed9t, \u0111\u01b0\u1eddng, mu\u1ed1i \u0103n v\u00e0 nh\u1eefng th\u1ef1c ph\u1ea9m th\u01b0\u1eddng d\u00f9ng h\u00e0ng ng\u00e0y kh\u00e1c. Ta th\u01b0\u1eddng th\u1ea5y tr\u00ean bao b\u00ec c\u00f3 ghi tr\u1ecdng l\u01b0\u1ee3ng r\u00f2ng ghi r\u00f5 kh\u1ed1i l\u01b0\u1ee3ng v\u1eadt ph\u1ea9m. Nh\u01b0ng c\u0169ng c\u00f3 c\u00e1c bao b\u00ec ghi tr\u1ecdng l\u01b0\u1ee3ng tinh 500 \u00b1 2 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_disable_autopaging":false},"categories":[15,9],"tags":[],"class_list":["post-7623","post","type-post","status-publish","format-standard","hentry","category-hoi-dap-khoa-hoc","category-toan-hoc"],"_links":{"self":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/7623","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/comments?post=7623"}],"version-history":[{"count":0,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/7623\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/media?parent=7623"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/categories?post=7623"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/tags?post=7623"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}