Thursday, June 21, 2012

Not "scientifically valid"

Sounds like some of the folks at the Douglas County (Colorado) School District could use a statistics refresher course. Writes the Denver Post:
The Douglas County School District has deemed its spring survey of parents "inconclusive" — a poll in which a majority of responding parents saw the district's suspended voucher program as "unfavorable" and expressed unhappiness with the district's overall direction.
District officials contend that not enough parents participated in the survey to make it a valid representation. As a result, they stamped every page of survey results posted on the district's website in red letters saying: "Inconclusive due to insufficient response rate."
More than 4,900 parents completed the survey. There are approximately 76,500 parents whose children attend Douglas County schools. 
[...]
District spokesman Randy Barber said the approximately 6 percent of parents who responded to the survey this spring was significantly under the 30 percent the district wanted to make it "scientifically valid."
Yes, people usually have more confidence in a survey if it has a higher response rate. But that doesn't mean that the results of this survey aren't valid, and there's nothing magic or "scientific" about the 30 percent threshold. We can conduct very accurate national surveys based on just 1,000 responses -- roughly a fifth of what they managed in this parent survey. More important than overall numbers is representativeness. That is, does the sample of parents who responded to the survey look roughly like the overall population within the school district? This can probably be figured out using demographic questions (although the only one I can find in the survey is just a race question. Area of residence, income, family size, ideology, etc., would be really helpful here.) 


Of course, maybe the reason that the district rejected the results as "inconclusive" has less to do with sample size than it does with the results, which were less than flattering for the district. If they really want to know what district parents think, they could conduct a survey of a representative (and probably smaller) sample and get solid results. But if they just want certain results, then by all means they should just keep doing surveys until they get the answers they want.

10 comments:

Joe said...

It doesn't help that there is no methodology section in the report. I wonder how much they were charged for this?

HưngTen said...

Actress Yoon Eun Hye recently updates her fans with a set of beautiful photos.


On August 16th, the actress uploaded the above photos on her Twitter with the short caption, “After the meeting.”

In the photos, Yoon Eun Hye is wearing black T-shirt while cutely leaning on a wooden bar. Calmly staring at the camera, she displays her well-defined girl dress
Parkland Isles Homes

job tracking software
boxdoccia

Interior Designer Miami
Remote Hosted Desktop

payday loans
home alarm services

payday loans
Windows Hosted Desktop

fashion eyeglasses
tailored Bespoke Suit

natural cure for cancer
erp software solution
Williamsburg VA Homes
Dog Day Care Business
cat posts
features and feminine charms, which captivated the public.
tute that conducts a scholastic ability test in mathematics, announced the result of the survey asking 220 students to vote for the celebrities who seem to be good/bad at math.

For the category askin
For the category asking student to vote for celebrities who seem to be good at math, actress Kim Tae Hee ranked first with 43.4% of the v
Netizens commented, “Yoon Eun Hye has become prettier,” “She looks lovely,” “Show us some of your good work” and “She looks innocent yet sexy.”

mostafashaban said...


شركة نقل عفش بالرياض تتمتع بمكانة مميزة بين جميع الشركات الكبرى التي توجد على مستوى مدن المملكة إذ حرصت دائما على أن تكون في خدمة عملائها على مدار 24 ساعة من خلال تخصيص خطوط خاصة للتواصل بالشركة والرد على ما يريده العميل واستقبال طلباتهم واستفساراتهم وشكواهم وبذلك استطاعت الشركة نيل ما وصلت له من سمعة ونجاح لا مثيل له عند تقديمها لخدمات نقل العفش من وإلى الرياض باستخدام الوسائل والمعدات الحديثة والتي من خلالها يضمن العميل نقل أثاثه ومحتويات منزله دون أن تتعرض لأية تلفيات أو خسائر فضلا عن توفير وقته وجهده وماله عند الاستعانة بخدمات شركتنا المميزة والاتصال بأرقام الخدمة المتاحة لجميع العملاء في أي وقت على مدار اليوم.
أبرز ما توفره شركة نقل عفش بالرياض من خدمات ومزايا
إذا قمت باختيار خدمات الشركة والاستعانة بعمالها في نقل عفشك فإنك بذلك قد ضمنت عملية نقل عفش آمنة و سريعة وخالية من الأخطاء حيث توفر الشركة ما يلي من خدمات:
1. يعمل أفراد فريق عمل الشركة بالتعاون سويا وبتنظيم وتنسيق تام بينهم من أجل أن يتم إنجاز الخدمات من نقل وتغليف وتنظيف وإعادة تركيب لمختلف أنواع الأثاث والمحتويات بجميع أنواعها، حيث أن الشركة تسعى دائما إلى أن يحصل العميل على السرعة والتميز في إنجاز كافة ما يتطلبه من خدمات.
2. توفر شركة نقل اثاث بالرياض خدمات نقل العفش للمنازل والبيوت والشقق والفلل والقصور والمكاتب والشركات وغيرها من المنشآت وتقديم عروض خاصة لعملائها الكرام ولأصحاب المساحات الشاسعة والأغراض المتعددة، كما أن الشركة تحرص على استخدام أدوات للتغليف تتناسب مع نوع وقيمة الأثاث الذي يتم نقله وتحرص على تغليف المحتويات الثمينة مثل اللوحات القيمة وغيرها بعناية شديدة.
https://www.allsaad.com/%D8%B4%D8%B1%D9%83%D8%A9-%D9%86%D9%82%D9%84-%D8%A7%D8%AB%D8%A7%D8%AB-%D8%A8%D8%A7%D9%84%D8%B1%D9%8A%D8%A7%D8%B6/

Anonymous said...

ما هي فروع سيتي بنك في السعودية؟!

카지노사이트탑 said...

Its awesome, I admire this blog here. Awesome article, keep doing it! thanks!

카지노사이트위키 said...

Awesome article dude! This was an extremely nice post. A top notch article

온라인카지노사이트 said...

I learned a lot in this blog. Thank you very much for sharing good content.

카지노사이트킹 said...

Useful blog information. Keep blogging! I wanted to thank you for this

파워볼사이트 said...

I will support you. Such a very useful article. A must read post, Thanks a lot

Anonymous said...

المتداول الخليجي من افضل المتداولين