Cau 39: Duong tan suat lyluan dua vao trong tinh toan tv dung de lam gi?Neu pp lua chon dang duong tansuat ly luan trong phan tich tv?

Duong tsll dung de xac dinh :luong dong chay bq nhieu nam Qn, he so phan tan Cv va he so ko doixung Cs trong do Qn =tong Qi/n

Cv=can bac 2 cua (tong(Ki-1)²/(n-1)):

Ki = Qi/Qn

Cs =tong( Ki-1)³ /(n-3).Cv³

De lua chon dang duong tan suat ly luan no phai la duong phu hop vpo mo ta dung dan nhat xu the bien thien cua gia tri thuy van theo tan suat xuat hien tuong ung the hien boi su phan bo cua "dam may" cac diem kinh nghiem

Cau40 viet cong thuc xac dinh cac tham so cua duong tan suat pIII theo pp mo men . khi nao co the dung pIII khi nao k ova cach khac phuc.

1) tinh Qn va sai so

Qn =Qi/n voi i=1- n .

Sai so tuong doi tinh theo cong thuc:

'Qn =Cv/n*100%

2) xac dinh he so phan tan Cv la thong so thong ke ko thu nguyen dac trung cho su phan tan cua dai luong ngau nhien theo thoi gian.

Cv=((Ki-1)^2/n-1)

Trong do Ki la he so mo dun Ki=Qi/Qn

Sai so tuong doi cua Cv: 'Cv=(1+Cv^2)/(2.(n-1))*100%

Neu sai so 'Cv<=10%-15% thi chuoi so lieu du dai.

3)he so ko doi xung Cs : khi chuoi so lieu du dai co the dung cong thuc gan dung de tinh Cs:

Cs=(Ki-1)^3/((n-3).Cv^3)

Sai so tuong doi tinh theo cong thuc:

'Cs=(6/n(1+6Cv^2+5Cv^4))/Cs.100%

Thuong thi Cs rat lon ta ko su dung gia tri Cs nay ma xac dinh Cs bang thud an ty so m=Cs/Cv.

• ve mat vat ly , de gia tri bien ngau nhien X phu hop voi cac dieu kien thuy van thi Cs>=2Cv. Khi Cs<2Cv thi chuyen sang dung ham Kriski- melken

Cau 41 mo ta cac buoc tien hanh de xay dung duong tan suat ly lua trong thuy van. Mot duong tan suat ly luan nhu the nao duoc coi la hop yeu cau.

De dung mot duong tan suat ly luan nao do ta lam theo cac buoc sau:

1) dung tri so Cv: Cv=((Ki-1)^2/n-1)

Ki la he so mo dun Ki=Qi/Qn

Gia thiet mot ty so m=Cs/Cv nao do tu 1 den 6

2)gia thiet su phan bo tan suat xuat hien cua dai luong thuy van dang xet xap xi voi mot dang phan bo tan suat nao do (pearsonIII hoac kritski- melken)

3 )vao bang phu luc "he so mo dun Kp" cua duong tan suat vua chon voi Cv va m tinh(noi suy) tung do cua duong tan suat ly luan ung voi cac gia tri tan suat theo cong thuc Qp=Kp.Qn

4 )cham diem tsll tren giay xac suat va ve duong cong tron di qua cac diem do keo dai cho den het to giay ta duoc 1 duong tsll.

5 )moi duog tsll dung tren mot giay xs rieng tren do phai co cac diem tskn da cham day du lam nen. Ky hieu tsll va tskn phai khac nhau.

* mot duong tsll dat yeu cau:la duong tsll di xuyen qua "dam may" cac diem tskn cu the tren tung doan duong nay so diem kinh nghiem nam ben trai va ben phai duong xap si bang nhau dau trenduong cong dig an sat voi cac diem kinh nghiem co gia tri lon nhat(nuoc lon ) dau duoi di gan sat cac diem kn co gia tri nho nhat.cua chuoi.

Tom lai duong tsll phu hop phai mo ta dung dan nhat xu the bien thien cua gia tri thuy van theo tan suat xuat hien tuong ung the hien bois u phan bo boi "dam may" cac diem kn noi tren.

Cau43 neu muc dich cua viec phan tich tuong quan trong huy van va cac quan he tuong quan hay duoc su dung.

Trong thuc te cac chuoi so lieu khi tuong thuy van thuc do tai cac tram vi nhieu ly do khac nhau qua ngan hoac bi dut quang dung luong ko du yeu cau cua phan tich mau thong ke=> nguoi ta nghi den tim mot quan he tuong quan nao do(tim ham tuong quan)giua cac dai luong dang xet voi cac dai luong khac co quan he ban chat voi dai luong dang xet nhung co so lieu du dai va dang tin cay qua do bo sung va keo dai chuoi so lieu dang xet.

Cac quan he tuong quan hay doc su dung:

1) quan he giua mua voi dong chay tren luu vuc(goi la quan he mua rao - dong chay)

2) Quan he giua dong chay voi cac yeu to khac nhu mua ,boc hoi , do day tham phu, tham..

3) Quan he luu luong (luong mua) giua tram tren va tram duoi

4) Quan he tuong quan cua 2 tram co nhieu quan he tuong dong .

Cau44 trinh bay pp tuong quan giai tich.va pp phan tich tuong quan do giai trong truong hop tuong quan tuyen tinh.

• pp phan tich tuong quan giai tich:

1)Phuong trinh hoi quy

-Duong hoi quy la duogn thang di giua cac diem thuc nghiem(xi,yi) va co dang y=ax+b

-pp giai tich ko tim cach ve duong thang hoi quy ma nham thong qua mot tieu chuan nhat dinh tren co so so lieu thuc do co han tim ra duogn thang phoi hop tot nhat dai bieu cho duog binh quan co dieu kien cua tong the noi tren.goi la Phuong trinh hoi quy.

- tieu chuan de xet duong hoi quy tot nhat hien nay la tong binh Phuong cac khoang lech la nho nhat: (yi-y)^2=(yi-(a+bxi))^2=Min

2) He so tuong quan.

De danh gia muc do tuog quan giua 2 bien (chat ,ko chat, ko tuong quan ) ta su dung he so tuong quan

=+-(xi-xtb)(yi-ytb)/(xi-xtb)^2(yi-ytb)^2 =+_(Kx-1)(Ky-1)/(Kx-1)^2(Ky-1)^2

Voi Kx=xi/x Ky= yi/y

Neu >0 tuong quan dong bien( mua nhieu=> dong chay nhieu)

<0 tuong quan nghich bien(boc hoi nhieu => dong chay it)

3) sai so tuogn quan

sai so noi o day la sai so cua Phuong trinh hoi quy , bieu thi bang sai so quan Phuong

Sy=(yi-y)^2/(n-1) y tinh theo x Sx= (xi-x)^2/(n-1) x tinh theo y

khi=+-1thi Sy ,Sx=o cac diem nam tren duong hoi quy

khi0<<1 thi tuong quan thong ke voi sai soSx va Sy

4)sai so cua he so tuogn quan

He so tuong quan do so lieu cua mau tinhra nen co sai so lay mau. Dung sai so tieu chuan bieu thi ta duoc:

=(1-^2)/n

*pp tuong quan do giai

Cach lam sau khi cham cac diem tuong quan (xi,yi) len he toa do vuong goc , neu cac diem nay tuong doi tap trung thanh mot dai hep va bao dam >=0.8 => ta co the ve mot duong thang di qua trrung tam cac nhom diem lam duong hoi quy de bo sung va keo dai so lieu

-De tranh tuy tien khi tra do thi ta co the viet ra pt tuong quan

y=ax+b

Hoac y=ax trong do b = diem cat truc oy a = hs goc cua duog thang tuong quan y = bien so can keo dai x= tri so bien so liet so lieu dai

-Truc toa do cua 2 diem thuoc duong tuong quant hay vao pt ta duoc he 2 pt giai ra duoc a va b

-pp nay don gian nhanh chong khac phuc duoc nhuoc diem cua pp giai tich la loai bo duoc cac diem phan tan bat thuong nhung co nhuoc diem lon la duong tuong quan chiu anh huong nhieu cua chu quan nguoi xac dinh no.

Cau 46: Chuoi so lieu dung de tinh dong chay nam can thoa man nhugn dieu kien nao?Neu cac buoc tinh toan dong chay nam truong hop chuoi so lieu du dai?

Xem cau 48