Usability measurement and metrics: A consolidated model
Ahmed Seffah · Mohammad Donyaee · Rex B. Kline ·Harkirat K. Padda 2006

Link
Several studies have reported the benefits of a strong commitment to usability in the software development lifecycle.
Several different standards or models for quantifying and assessing usability have been proposed within the Human-Computer Interaction (HCI) and the Software Engineering (SE) communities. Examples of the latter include the ISO/IEC 9126-1 (2001) standard, which identifies usability as one of six different software quality attributes; the ISO 9241-11 (1998) standard, which defines usability in terms of efficiency, effectiveness, user satisfaction, and whether specific goals can be achieved in a specified context of use; and Directive 90/270/EEC of the Council of the European Union (1990) on minimum safety and health requirements for work with computers.
Motivations for a consolidated model for usability measurement are to:
1. Reduce the cost of usability testing.
2. Complement more subjective evaluations.
3. Help in comminication of usability measurement.
4.Promote good usability measurement practises.

This paper evaluates the existing usability measurement standards or models very well and this could be done in our literature review:
1 Usability in ISO standards related to HCI
2 Usability in traditional software quality models
3. Other specific measurement models

The paper gives three main reasons for a consolidated model:
1. The hierarchical quality models has some common limitations
2. Most of the software quality models are static
3. It can be rather difficult to apply usability standards in practice, that is, to decide exactly how to measure the usability of a particular application

This paper proposes QUIM (Quality in Use Integrated Measurement) as a consolidated model for usability measurement. Quim consists of several aspects including:
1. User model, context of use and usability in context
2. Usability factors(which is divided into ten factors
3. Measurable criteria
4. Metrics

Some uses of quim would would be: 1. Gives consistent definitions of usability factors, criteria, and metrics; and 2. Maps the hierarchical relations among them. It is also intended to serve as a guide in planning for usability measurement.
They developed aq "quim editor" program to support the uses described in this paper.

A comparison of current approaches to usability measurement
Dr J Kirakowski & Dr R Murphy 2009
link
This paper looks at how 15 different organisations evaluate percieved usability. The results are centered around presentations made each other at the Usability Professionals' Association (UPA) workshop in 2009. This a preliminary paper with a follow on planned.
The Comparative Usability Evaluation (CUE) seminars are a series of occasional seminars organised by Prof. Rolf Molich and colleagues at the UPA conferences since 1998. The first CUE result suggested that some usability experts found the use of statistical data difficult. The latest CUE seminar(the 8th)is more concerned with measurement methods of usability, where when a website is redone it can compared to the measurement of its previous incarnation.
The requirements were fairly strict in that were five tasks to be carried out by end users on the web site. For each task, the following measures had to be taken:
1. Time on task (efficiency)
2. Success (effectiveness)
The results were divided into different sections:
1. Context of Use
The ISO 9241 definition of usability states that usability may only be meaningfully measured in context. For most the users demographic data was not gathered, and for some no knowledge of participants were known. Six groups used a remote unattended methodology by which it is meant that users interacted with the web site at home on their own computers, onto which a test suite had been downloaded. Some used naturalistic setting and some a laboratory setting
2. Sample Size
the largest was 314. Smallest was 9. Average was 20.
3. Effectiveness
Some measured effectiveness in boolean style while others. Measured success as a percentage.
4. Efficiency
Most common measurement of efficiancy was a time task. A ping methodology was also used.
5. Satisfaction
Questionaires (SUS) were used by many to evaluate. However this data shows that SUS is strongly skewed towards the high numbers when applied to web sites and although its range is transformed to the interval {0:100} only 40 discriminations are possible.A false sense of optimism can be presented from the WAMMI questionnaire. Usability score. This corresponds well with user comments as reported by all the groups.

All the mainstream measures reviewed in this paper have exhibited major conceptual flaws in terms of measurement. We also recommend that either more work be done to create a well-validated questionnaire for user satisfaction with web sites that is public domain. The way data is gathered by remote unattended testing methodologies at present is not controlled in terms of precision and we recommend that a greater emphasis be placed in remote unattended testing on data verification.

The Self-Confrontation Interview: Towards an Enhanced Understanding of Human Factors in Web-Based Interaction

This paper studies the effects on a user while they are on the Internet doing normal activities such as purchasing products through self-confrontation interview.
The self-confrontation interview comprises the following steps

• Asking subjects to perform the behavior being analyzed;
• Making a video-recording of the subjects’ actions;
• Asking the subjects to view the video recordings of their own actions;
• Pausing the video recordings at certain junctures and asking the subjects to recount any thoughts and emotions they had when they performed those actions;
• Transcribing the interviews and correlating the actors’ thoughts and emotions with their respective actions

Paper Here

Dimensional Hierarchy of Retail Website Quality

This paper studies the most important factors in an users experience of website quality and how a hierarchy of elements of quality can be developed. It uses Loiacono's WebQual scale to examine the dimensional hierarchy of the quality of apparel websites.
Customers satisfaction is very important while using a website or they will not return. Researchers from several disciplines have developed and tested instruments to measure website quality.  In this paper the authors propose their own model of hierarchy regards website quality and compare it with other models.  They propose a model of 6 factors that effect website quality from a users perspective.  These are

1. Information
2. Ease of Use
3. Entertainment
4. Trust
5. Transaction
6. Consistent Image

Paper can be found here Link.

A Comparison of Questionaires Thomas S. Tullis & Jacqueline N. Stetson UPA 2004 funded by Fidelity Investments Variety of questions have been reported in the literature for assessing percieved usability. Worrys about effectiveness of these questions was the reason for this study. Quesionaires used were: 1. System Usability Scale(SUS) 2. Questionaire for User Interface Satisfaction 3. Computer System Usability Questionaire 4. Words 5. Fidelity Investments own questionaire The study was carried out online on fidelity investments intranet 123 participants. Two sites used were: 1. finance.yahoo.com 2. kiplinger.com The users were asked to carry out to tasks. 1. Find the highest price in the past year for a share. 2. Find mutual fund with the highest 3 year return. Overall score was generated by converting each questionaires score to a percentage. All 5 showed site 1 to score higher. Although the accuracy of the results would have been better with a larger dataset. Also only two sites and two tasks gave limited results. It is also easier to compare to sites to each other than it is to evaluate a stand alone website. I found this paper a little limited in the the depth it went into the subject.

Measuring Percieved Website Usability 2007 Jianfeng Wang & Sylvain Semeca Journal of Commerce 2007 This paper tried to develope a short reliable and valid percieved website usability measurement scale(parimonious scals usable across all websites). There is an argument to be made that users experience a website before they commit to use it. Usability defined as how well and how a user, without training can interact with an information system of a website. A website must be compatible with characteristics of human action and perception, but also with users cognitive skills in communication, understanding, memory, and problem solving. In the usability metrics section of the paper it states there are five distinct approaches of usability testing: 1 Testing, 2 Inspection 3 inquiry, 4 Analytical modelling, 5 simulation. All dependent on subjective assessments in the form of user judgement. There are three dimensions of usability: 1. Ease of use 2. Navigation speed 3.Interactivity This paper also states the the fact a positive correlation exists between the usability construct and attitude towards the website. The method used involved 350 students asked to go to transactional website and perform set tasks. It tried to focus one dimension at a time. Future directions suggests looking at testing the scale in relation to different contexts such as informational websites destined for professional buyers. This scale is good in identifying which of the dimensions of a website need tob improved. The limitations of the study are that it was used only one website and mightent have great generalizability. Also cannot be certain users experienced all functionality of the website. future directin of research suggested by this paper could be look at subjective versus objective approaches of usablity evaluation.

The impact of external reference price on consumer price expectations Praveen K. Kopalle, Joan Lindsey-Mullikin This paper is relevant to the low initial quote(on an external reference) followed by a higher quote once the consumer visited the actual source.